day

day — noun

1. a unit of time equal to 24 hours, starting at midnight and ending at the followi

1.nounA1
Definition

a unit of time equal to 24 hours, starting at midnight and ending at the following midnight — the length of one full rotation of the Earth.

Example

There are seven days in every normal week.

Chidi's birthday party will start in three days.

day + in + future time period

Common collocations
  • per day
  • the next day
  • every day
  • within a day
  • the following day
Synonyms
  • 24 hours

    more precise and technical; used in medical or scientific contexts

Antonyms
  • night

    refers to the dark period, while 'day' here includes both day and night

Grammar Patterns

day + of + month/event

number + day(s) + ago/later

per day / a day

Usage Note

The most basic sense of 'day'. When counting days, no preposition is needed before 'day' with time expressions: 'I'll be there Monday' (not 'on Monday' in informal use), but 'in three days' refers to the future, and 'three days ago' refers to the past.

Common Mistakes

I will come after three days.
I will come in three days.
In English, 'after three days' is unusual for future plans; use 'in three days' to mean 'three days from now'.
I stayed there for three days ago.
I stayed there for three days.' or 'I was there three days ago.
Do not combine 'for' and 'ago' in the same time expression.

2. the light part of a 24-hour day, when the sun is up and the sky is bright — used

2.nounA2
Definition

the light part of a 24-hour day, when the sun is up and the sky is bright — used to contrast this period with the night or the dark.

Example

Owls sleep during the day and hunt at night.

during the day / at night contrast

The museum is open every day from nine in the morning until five in the afternoon.

Common collocations
  • during the day
  • by day
  • all day long
  • day and night
  • in broad daylight
Synonyms
  • daylight

    specifically the natural light of the day, not the period itself

  • daytime

    interchangeable with 'day' in this sense; slightly more formal

Antonyms
  • night

    the dark period between sunset and sunrise

Grammar Patterns

during the day

by day

all day (long)

Usage Note

Use 'during the day' or 'in the daytime' to refer to the light period. 'By day' is a slightly more formal or literary alternative. 'All day' means the entire daylight period, often with an implication of continuous activity.

Common Mistakes

I work at day.
I work during the day.
The preposition 'at' is not used with 'day' in this sense; use 'during the day' or 'in the daytime'.
The whole day I was tired.
I was tired all day.' or 'The whole day, I was tired.
In natural English, 'all day' is more common than 'the whole day' as an adverb.

3. the hours that a person spends at their job or in classes, as opposed to their f

3.nounA2
Definition

the hours that a person spends at their job or in classes, as opposed to their free time or time spent sleeping.

Example

Sari has a very long day at school on Mondays.

a + adjective + day + at + [place]

After a hard day at the office, Emre likes to go for a run.

Common collocations
  • working day
  • school day
  • long day
  • hard day
  • day off (opposite)
Synonyms
  • working day

    specifically a day spent at work, not school

  • workday

    American English term for working hours at a job

Grammar Patterns

a + long/busy/hard + day

day + of/at + [place]

my/your/his + day

Usage Note

'How was your day?' is a very common A1 greeting used between people who know each other, especially family members or colleagues. 'A hard day' and 'a long day' are fixed collocations meaning a tiring day.

Common Mistakes

How is your day?' (as a greeting after the day is finished).
How was your day?
Use past tense when asking about a day that has already happened or is ending.
I have a busy day today.' (grammatically correct but less natural).
I have a busy day ahead.' or 'It's a busy day for me.
These are more natural ways to describe a currently busy day.

4. a day when a person does not have to go to work, attend school, or do their usua

4.nounB1
Definition

a day when a person does not have to go to work, attend school, or do their usual duties, often for rest or personal activities.

Example

Bao took a day off to go to the dentist.

take + a day off + to + [verb]

Fridays are Maja's day off from the café.

day off + from + [place/work]

Common collocations
  • day off from
  • take a day off
  • have a day off
  • ask for a day off
  • my day off
Synonyms
  • holiday

    British English: a day off from work or school; in American English, 'holiday' means a special celebration day

  • time off

    broader term that can cover hours, days, or weeks away from work

Antonyms

Grammar Patterns

a + day + off

have/take + a day off

my/your/his + day off

Usage Note

The phrase 'day off' uses 'off' as an adverb, not a preposition. When specifying the place, use 'from': 'a day off from work/school'. 'Have a day off' is more common in British English; 'take a day off' is common in both British and American English.

Common Mistakes

I have a rest day.
I have a day off.
'Day off' is the standard expression for a non-working day. 'Rest day' is only used for sports training schedules.
I had a day-off yesterday.
I had a day off yesterday.
Do not hyphenate 'day off' as a noun phrase.

5. a short time in the recent past, usually two to five days before the present mom

5.nounB1
Definition

a short time in the recent past, usually two to five days before the present moment, used in fixed phrases like 'the other day' or 'a few days ago'.

Example

I saw Lukas at the train station the other day.

the other day = a few days ago

Otis called me a few days ago about the school reunion.

a few days ago — exact time reference

Common collocations
  • the other day
  • a few days ago
  • just the other day
Synonyms
  • recently

    can refer to any time in the recent past, from hours to weeks ago

  • a short time ago

    more general than 'the other day'; can refer to hours or minutes ago

Grammar Patterns

the other day

a few days ago

these past few days

Usage Note

'The other day' is an indefinite reference meaning 'a few days ago' — the speaker does not need to specify which day. 'A few days ago' is more precise. Both are used with past tense verbs. This sense does not have a plural form.

Common Mistakes

I met him the other day ago.
I met him the other day.
'The other day' already implies a past time; do not add 'ago'.
I saw her in these days.
I saw her the other day.
'In these days' is not used for recent past events in English.

6. the present period of time or the modern age, used especially when comparing how

6.nounA2
Definition

the present period of time or the modern age, used especially when comparing how life is now with how it was in an earlier time.

Example

Kids these days spend a lot of time on their phones.

kids/people + these days — comparing to past

In my grandmother's day, people sent letters by post.

in + someone's + day — past era reference

Common collocations
  • these days
  • in those days
  • in my day
  • back in the day
  • in someone's day
Synonyms
  • nowadays

    interchangeable with 'these days' but slightly more formal

  • today

    broader; can mean 'on this current day' or 'in modern times'

Antonyms
  • in the past

    refers to earlier periods, the opposite of modern times

Grammar Patterns

these days

in those days

in my day

back in the day

Usage Note

'These days' contrasts the present with the past. 'In my day' refers to a period when the speaker was younger and is nostalgic or critical. 'Back in the day' is informal and nostalgic, common in American English. 'In those days' points to a specific past period.

Common Mistakes

In these days, technology is changing fast.
These days, technology is changing fast.
Do not use 'in' before 'these days' when it means 'nowadays'.
It was very different in my days.
It was very different in my day.
'In my day' is a fixed singular phrase, even though it refers to a period of many years.

7. used to refer to a period in the past, especially one that the speaker remembers

7.nounB2
Definition

used to refer to a period in the past, especially one that the speaker remembers or that older people have described — for example, talking about life before modern technology.

Example

In those days, people had to walk miles to fetch water from the nearest well.

in those days + past-era collocation

Christopher's grandmother says that in the old days, children ate whatever was put on the table.

in the old days expressing remembered past

Common collocations
  • in those days
  • in the old days
  • in my day
  • back in those days
Synonyms
  • era

    more formal and denotes a longer, well-defined historical period

  • time

    broader and less specific; 'in my time' overlaps but sounds slightly older in style

Antonyms
  • present

    the current period, contrasted with past eras

Grammar Patterns

in those days

in the old days

in those + noun + days

Usage Note

Frequently paired with a possessive determiner or noun modifier: 'in my day', 'in those days', 'in the old days'. Not typically used alone as a simple adverb — the phrase structure is required.

Common Mistakes

Day, people walked everywhere.
In those days, people walked everywhere.
'in those days' or 'in the old days' is the required fixed phrase, not just 'day' alone.

8. used to say that something is expected to happen soon, usually in the coming day

8.nounB2
Definition

used to say that something is expected to happen soon, usually in the coming days — for example, waiting for news, a delivery, or a natural event.

Example

The baby is due any day now, so Camila has packed her hospital bag.

any day now for expected events

The repair crew said they would come any day now to fix the broken pipe.

Common collocations
  • any day now
Synonyms
  • soon

    sooner range is vaguer; 'any day now' adds a concrete sense of days, not weeks

  • momentarily

    more formal and suggests happening at any moment, not necessarily within days

Antonyms
  • never

    complete opposite of expected future event

Grammar Patterns

any day now

Usage Note

Almost always used with future or present tense. Never used for past events. The phrase carries a tone of hopeful or confident expectation.

Common Mistakes

I graduated any day now.
I expect to graduate any day now.
'any day now' refers to a future event, not a past one.

9. the outdoor period when there is natural sunlight, thought of as the time for be

9.nounB1
Definition

the outdoor period when there is natural sunlight, thought of as the time for being outside, travelling, or doing activities without needing artificial light.

Example

Feng prefers to study by day and relax in the evening.

by day as adverbial phrase

The museum is open during the day but closes at five o'clock.

during the day for opening hours

Common collocations
  • by day
  • during the day
Synonyms
  • daytime

    the noun form; used in 'in the daytime' adverbial phrases

  • daylight hours

    more formal and emphasizes the natural-light aspect

Antonyms
  • night

    the period after sunset

Grammar Patterns

by day

during the day

Usage Note

Distinguish from noun sense 2 (DAYTIME HOURS): sense 2 contrasts day-as-light with night-as-dark within a single 24-hour cycle; this sense treats daylight as the outdoor-activity window. 'By day' and 'during the day' are the most common adverbial patterns.

Common Mistakes

I work in day.
I work during the day.
'in day' is ungrammatical; use 'during the day' or 'by day'.

10. happening every single day, especially in a way that feels boring, tiring, or un

10.nounB1
Definition

happening every single day, especially in a way that feels boring, tiring, or unpleasantly repetitive.

Example

Eleni got tired of eating the same lunch day after day.

day after day expressing boredom with repetition

Nkechi walked the same route to the factory day after day for twelve years.

Common collocations
  • day after day
Synonyms
Antonyms

Grammar Patterns

day after day

day after day + clause

Usage Note

This fixed phrase carries a negative or weary tone — it emphasizes monotony or hardship. Use 'every day' for neutral repetition. 'Day after day' can appear at the start or end of a clause.

Common Mistakes

I go to school day after day and I enjoy it.
I go to school every day and I enjoy it.
'day after day' sounds complaining; use 'every day' for neutral or positive contexts.

11. throughout the whole time from morning until night, without stopping or taking a

11.nounA2
Definition

throughout the whole time from morning until night, without stopping or taking a break.

Example

Dario sat at his desk all day long finishing the report for his manager.

all day long for continuous work

The children played outside all day long and came home covered in mud.

Common collocations
  • all day long
  • all day
Synonyms
Antonyms
  • briefly

    for a short period, opposite of the whole day

Grammar Patterns

all day long

all day

Usage Note

'All day long' is more emphatic than 'all day' and often appears in informal or narrative contexts. Both forms are interchangeable in most situations.

Common Mistakes

I was studying all the day long.
I was studying all day long.
'the' is not used between 'all' and 'day' in this pattern.

12. happening slowly and continuously, so that a change is more noticeable from one

12.nounB2
Definition

happening slowly and continuously, so that a change is more noticeable from one day to the next — often used for improvements, growth, or gradual decline.

Example

Owen's health improved day by day after he started the new treatment.

day by day describing gradual improvement

The pile of paperwork on Eli's desk grew day by day.

day by day describing gradual increase

Common collocations
  • day by day
Synonyms
  • gradually

    adverb that captures the slow-change aspect without the daily rhythm

  • little by little

    more informal and can apply to any unit of time, not just days

Antonyms
  • suddenly

    implying an immediate change, the opposite of gradual

Grammar Patterns

day by day

day by day + clause

Usage Note

Emphasizes a gradual, cumulative change — unlike 'every day', which can imply a repeated identical action. 'Day by day' is often used with verbs of change: improve, grow, rise, weaken, recover.

Common Mistakes

I brush my teeth day by day.
I brush my teeth every day.
'day by day' emphasizes change over time, not simple daily repetition.

13. Used to describe something that varies or keeps changing, so that it is not the

13.nounB2
Definition

Used to describe something that varies or keeps changing, so that it is not the same on any two days in a row.

Example

The weather in this mountain city changes from day to day, so always carry an umbrella.

change (from) day to day — variability

Noor's appetite varies from day to day, which makes meal planning difficult.

Common collocations
  • change (from) day to day
  • vary (from) day to day
  • differ (from) day to day
  • shift (from) day to day
Synonyms
  • vary

    Broader term — can apply to any kind of difference, not limited to time

  • fluctuate

    More formal; implies alternating up-and-down movement

  • shift

    Suggests movement from one state to another, often gradually

Antonyms

Grammar Patterns

(from) day to day

change (from) day to day

vary (from) day to day

Usage Note

The subject of this phrase is typically something variable: weather, mood, prices, conditions, or other changing situations. The word 'from' is often dropped, especially in informal speech: 'changes day to day'.

Common Mistakes

The menu changes from day to day to day' (extra 'to day').
The menu changes from day to day.
The fixed phrase contains only two occurrences of 'day'.

14. The day that comes immediately before a particular date, event, or point in time

14.nounB1
Definition

The day that comes immediately before a particular date, event, or point in time.

Example

Amihan studied all afternoon the day before the final chemistry exam.

the day before + [event]

The shop closes at noon on the day before a national holiday.

Common collocations
  • the day before yesterday
  • the day before [event/date]
  • the day before that
Synonyms
Antonyms

Grammar Patterns

the day before + [event]

the day before + [date]

the day before yesterday

Usage Note

This phrase functions as an adverbial noun phrase — no preposition (in/on) is needed. It is often followed by 'of' plus a specific event: 'the day before of the wedding' is incorrect; use 'the day before the wedding'.

Common Mistakes

I met her the day before of the party.
I met her the day before the party.
Do not insert 'of' after 'the day before'.

15. A past era or memorable stage in history or in someone's life, especially one th

15.nounC1
Definition

A past era or memorable stage in history or in someone's life, especially one that feels quite different from the present.

Example

Back in the day, people relied on paper maps instead of phone apps for directions.

back in the day — informal time reference

Lisa recalls that back in the day, her neighbourhood had only one small grocery store.

Common collocations
  • back in the day
  • in those days
  • in the days of
  • in someone's day
  • the days when
Synonyms
  • era

    Typically refers to a longer, named period (e.g. 'the Victorian era')

  • age

    More formal; often used with a specific label (e.g. 'the digital age')

  • times

    Informal plural; 'in those times' is similar to 'back in the day'

Antonyms
  • the present day

    The current period, in contrast with a past era

  • today

    Simple, direct antonym for 'back in the day'

Grammar Patterns

back in the day

in those days

in someone's day

in the days of

Usage Note

'Back in the day' is informal and used for nostalgic recollection. More formal alternatives include 'at that time' or 'in that era'. 'In someone's day' refers to the period when that person was active or young. Distinguished from noun/7 'in the past' which is a general time reference without nostalgic or era-specific connotations.

Common Mistakes

Back in the days, we walked to school.
Back in the day, we walked to school.
The fixed phrase uses the singular 'day', not 'days'.

16. Still true or continuing right up to the current time, even though a long period

16.nounB2
Definition

Still true or continuing right up to the current time, even though a long period has passed.

Example

To this day, no one knows what started the fire that destroyed the old library.

to this day — sentence-initial position

Christopher feels guilty to this day about breaking his sister's favourite doll.

Common collocations
  • to this day
Synonyms
  • still

    Simpler and less emphatic; common in everyday speech

  • even now

    Similar emphasis to 'to this day', slightly more dramatic

  • yet

    Used only in negative or question contexts: 'has not happened yet'

Antonyms

Grammar Patterns

to this day

Usage Note

Often used at the start or end of a clause for emphasis. Stronger and more emphatic than 'still' because it stresses the entire duration that has passed. Works in both positive statements and negative ones.

Common Mistakes

I to this day haven't finished reading that book.' (awkward placement).
To this day, I have not finished reading that book.
'To this day' is typically placed at the beginning or end of a clause, not in the middle.
Idioms

Something that is a normal part of your job and not surprising.

For a firefighter, rescuing a cat from a tree is all in a day's work.

Dealing with difficult customers is all in a day's work for Sara.

Very soon, possibly at any moment.

The package should arrive any day now.

We expect the test results any time now.

Used to introduce the most important point after considering everything.

At the end of the day, we all want the same thing.

At the end of the day, it's your choice.

In the past, especially a time that is remembered fondly.

Back in the day, we used to play outside until dark.

My grandfather often talks about how cheap things were back in the day.

At a particular time in the past.

Back in the days when I was a student, I had more free time.

Back in the days of black-and-white TV, life seemed simpler.

The time in the early morning when light first appears.

We set out on our hike at break of day.

The birds start singing at break of dawn.

To decide to stop working or doing an activity for the rest of the day.

After finishing the report, Brian decided to call it a day.

It's getting dark, so let's call it a day and go home.

To be successful in a competition, argument, or struggle.

Despite the odds, the underdog team carried the day.

Patience and hard work can win the day.

Very easy to see, understand, or recognize.

The instructions were as clear as day.

Her guilt was clear as day from the evidence.

Continuously for many days, often in a boring or annoying way.

She does the same routine day after day.

Day after day, the rain continued without stopping.

All the time; without stopping.

The factory operates day and night.

She studied day and night for the final exam.

Gradually, as each day passes.

Day by day, the patient's condition improved.

The city is changing day by day.

Every day for a long period of time, often in a boring way.

He works at the same desk day in, day out.

Day in, day out, she takes the same bus to work.

The time when someone must face the consequences of their actions.

The day of reckoning came when the bills arrived.

He knew a day of reckoning was coming for his lies.

Someone or something will not continue to exist or be successful for much longer.

The old building's days are numbered; it will be demolished soon.

His days as manager are numbered after that loss.

To spend the last part of your life in a particular condition or place.

She ended her days in a small cottage by the sea.

He ended his life in peace after a long illness.

Everyone will have a time of success or good luck at some point.

Don't worry, every dog has his day.

She finally won the lottery; every dog has its day.

The time when you must do something unpleasant or difficult.

I kept putting off the evil hour of cleaning the garage.

The evil day arrived when he had to give his speech.

The recommended daily amount of fruits and vegetables for good health.

Try to eat five a day for better health.

She starts her five a day with an apple at breakfast.

From the very beginning.

From day one, the project was doomed to fail.

She was a great leader from day one.

Without planning for the future; living in the present.

They live from day to day, not knowing what will happen.

His mood changes from day to day.

Used to describe a situation that changes often and is uncertain.

The weather changes from one day to the next.

I never know what to expect from one day to the next.

Starting from that day and continuing into the future.

From that day forth, they were best friends.

From that time forth, he never touched alcohol again.

A helpful or kind action that you do, often as part of a routine.

I helped an old lady cross the street; that's my good deed for the day.

She donated to charity and felt she had done her good deed for the day.

A past time that is remembered as either better or worse than the present.

Grandpa often talks about the good old days.

The bad old days of war are behind us.

To no longer be successful, popular, or powerful.

That actor has had his day; he rarely gets roles now.

The old technology has had its day.

A friendly way to say goodbye, especially to customers.

The cashier smiled and said, "Have a nice day!"

Have a nice day! See you tomorrow.

To be in poor condition, especially from age or use.

This old sofa has seen better days.

My car has known better days; it's falling apart.

Used to emphasize that someone is at least a certain age.

She must be sixty if she's a day.

He's seventy if he's a day.

Used to express surprise at something you have never experienced before.

I've never seen such a mess in all my born days.

In all my born days, I've never heard such nonsense.

When you think about something calmly and clearly, especially after time has passed.

In the cold light of day, the problem seemed less serious.

The decision looked foolish in the cold light of day.

During the time when someone was most successful, famous, or active.

In my grandmother's day, people wrote letters by hand.

He was a great athlete in his day.

A long time ago in the past, often used when telling stories.

In the olden days, people traveled by horse.

What was school like in the olden days?

In the present time, especially compared to the past.

In this day and age, everyone has a smartphone.

It's surprising that such poverty still exists in this day and age.

Used when several bad things happen to someone on the same day.

First I lost my keys, then I missed the bus—it's not my day.

It's just not your day, is it?

Too late to take effective action or change a situation.

He started studying late in the day and failed the exam.

It's a bit late in the day to apologize now.

The entire day, often used to emphasize length.

She worked in the garden the livelong day.

He sat and watched TV the livelong day.

To survive a failure or setback and have another chance in the future.

We lost the match, but we live to fight another day.

The company went bankrupt, but the owner lived to fight another day.

To make someone very happy on a particular day.

Getting a surprise gift really made my day.

Your kind words made her day.

To spend the whole day or evening enjoying a particular activity.

We went to the beach and made a day of it.

They decided to make a night of it and went dancing.

All the time; continuously.

The machines run night and day.

She worked night and day to finish the project.

Something that attracts attention for a short time and then is forgotten.

The celebrity scandal was a nine days' wonder.

That new gadget will be a nine days' wonder.

To refuse to speak to or acknowledge someone because you dislike them.

Since the argument, she won't give him the time of day.

The popular kids wouldn't give me the time of day.

To not have much time; to be in a hurry.

Come on, we don't have all day!

Hurry up, I don't have all day to wait.

Belonging to the period when someone lived or was active.

Shakespeare was the greatest writer of his day.

The fashion of her day was very different.

Relating to the present time or a specific day.

The soup of the day is tomato basil.

The news of the day was all about the election.

one day

idiom

At some time in the future or on a particular day in the past.

One day, I hope to travel around the world.

One day, she walked into the room and announced her engagement.

At some time in the near future.

One of these days, I'll learn to cook.

One of these days, you'll regret that decision.

A day when many things go wrong.

It's been one of those days where nothing goes right.

I spilled coffee on my shirt; it's one of those days.

The typical or expected thing at a particular time or occasion.

Casual dress is the order of the day at this company.

Efficiency was the order of the day during the project.

To have a short, friendly conversation with someone.

I stopped to pass the time of day with my neighbor.

She passed the time of day with the shopkeeper.

Used to say that important things take time and cannot be done quickly.

Don't rush; Rome wasn't built in a day.

Learning a language takes time—Rome wasn't built in a day.

The time when you are young and inexperienced.

In my salad days, I made many mistakes.

She often looks back on her salad days with fondness.

To prevent failure or disaster when it seems certain.

The firefighter saved the day by rescuing the cat.

Her quick thinking saved the situation.

At an unknown time in the future.

Some day, I will visit Japan.

Some day, we'll look back and laugh at this.

To deal with the present moment without worrying about the future.

After the accident, she took things one day at a time.

We don't know what will happen, so let's take it one day at a time.

Used to say that something is very unlikely to happen.

You clean your room? That'll be the day!

He apologizes? That'll be the day.

In the present time, especially compared to the past.

These days, most people have smartphones.

Kids grow up so quickly these days.

Used to say that a past time was better or happier than the present.

Remember when we were carefree? Those were the days.

Those were the days when music was simple.

Exactly (used with periods of time).

It's been three years to the day since we met.

He died 50 years to the day after his birth.

Even now, after a long time has passed.

To this day, I still remember her name.

To this day, the mystery remains unsolved.

Used to show strong feelings like surprise, shock, or annoyance.

Oh my days! I can't believe you won the lottery.

Oh my days, did you see that huge spider in the bathroom?

day — biographical name

Word family

Synonym discussion

Sense: noun/1

Day (noun/1) refers to a full 24-hour cycle, from midnight to midnight. '24 hours' is its exact technical equivalent, used in medical, scientific, and logistics contexts ('the medication must be taken every 24 hours') — but it is less natural in everyday conversation ('see you in a day' sounds normal; 'see you in 24 hours' sounds clinical). 'Date' refers to a specific calendar day identified by number, month, and year ('What is today's date?'), so it overlaps with 'day' only when the speaker needs to pinpoint a calendar slot rather than a time span. 'Daytime' is narrower: it covers only the light period within the 24-hour cycle, not the night. For example, 'I work during the day' and 'I work during daytime' are similar, but 'I stayed for three days' cannot be replaced with 'three daytimes'.

Common collocations

Nouns

  • day job
  • day trip
  • day care
  • day shift
  • day school
  • opening day
  • closing day
  • due date (day)

Adverbs

  • all day
  • every day
  • the next day
  • the following day
  • the previous day
  • one day

Phrases

Prepositions

  • by day
  • during the day
  • per day
  • within a day
  • in + someone's + day
  • on + day + (of week/event)

Etymology

Proto-Indo-EuropeanProto-GermanicOld EnglishMiddle EnglishEnglish

The word 'day' comes from Old English dæg, which meant both 'the period of sunlight' and 'the 24-hour cycle'. It traces back through Proto-Germanic *dagaz to the Proto-Indo-European root *dhegʷh-, meaning 'to burn' or 'to be warm' — a clue that the earliest sense referred to the warm, sunlit part of the cycle. Cognates include German Tag, Dutch dag, and Old Norse dagr. The modern spelling settled in Middle English, and the daylight-versus-24-hour ambiguity has been part of the word since its earliest recorded use.