thin
thin — verb
1. to add water or another liquid to a thick substance so that it becomes less thic
to add water or another liquid to a thick substance so that it becomes less thick and flows more easily
Talia thinned the dark paint with water before brushing it onto the wall.
transitive: thin + noun + with + noun (liquid agent)
The gravy was too thick, so Diya thinned it with a little milk.
passive: 'was thinned'; 'by -ing' clause for method
If the paste feels too stiff for the paper, thin it slowly with warm water.
imperative: 'thin it + with'
Sana thins her oil paints with a blending medium, then builds up soft layers of colour on the canvas.
As Noa brushed the wood glue onto the joint, it thinned quickly and soaked deep into the grain.
intransitive: 'thinned' without object, describing a natural process
- thin with water
- thin with milk
- thin with broth
- thin to the consistency of…
- thin to a smooth paste
- dilute
more formal or scientific; used in chemistry and cooking
- water down
informal; often implies making something weaker or less acceptable
- weaken
focuses on reduced strength or concentration rather than consistency
- thicken
the opposite action; to make a substance more thick and less liquid
Grammar Patterns
thin + noun + with/by + noun (transitive)
thin + adverb/prepositional phrase (intransitive)
Usage Note
This sense can be transitive (thin + object) or intransitive (the substance thins on its own). The liquid agent is introduced with 'with' or 'by -ing'. Intransitive uses are less common and usually describe a natural process (e.g., paint thins as it warms).
Common Mistakes
2. to become smaller in number, or to remove some items from a group so that the re
to become smaller in number, or to remove some items from a group so that the remaining items have more room to grow or exist
The crowd outside the theatre thinned quickly after the final curtain came down.
intransitive: crowd + thins
Putri thinned out the carrot seedlings so the strongest plants would have room to grow.
transitive: thin + out + noun (gardening)
As midnight approached, the number of guests at the party began to thin noticeably.
intransitive with 'begin to': number + thins
The gardener thinned the lettuce rows to give each head enough space and sunlight.
transitive without 'out': thin + noun (gardening)
Traffic on the highway usually thins out after the evening rush hour ends.
intransitive with 'out': traffic + thins out
- thin out
- thin the seedlings
- thin the rows
- thin the herd
- thin to one plant per pot
- begin to thin
Grammar Patterns
thin (out) (intransitive) — subject is a crowd/group
thin + noun + out (transitive) — object is plants/seedlings/crowd
Usage Note
Frequently used with 'out', especially in conversation. The intransitive use describes crowds, traffic, hair, or any group becoming less dense. The transitive use is common in gardening and forestry, where a gardener removes some plants so the rest have more room.
Common Mistakes
thin out
phrasal verbto become fewer in number, or to remove some items from a group to create more space — used especially for crowds, traffic, or plants in a garden
The crowd began to thin out around midnight after the fireworks display ended.
Élise thinned out the young apple trees so the strongest ones would produce bigger fruit.
thin — adjective
1. measuring very little from one flat side to the other, so that something is not
measuring very little from one flat side to the other, so that something is not thick — for instance, a slice of bread, a layer of paint, or a wall.
The ice on the pond was too thin for anyone to walk on.
predicative use with too
Jabari cut the cheese into thin slices for the sandwiches.
attributive: thin + noun (slices)
A thin layer of dust covered every surface in the old library.
collocation: thin layer
The walls in Andrei's apartment were so thin that he could hear his neighbours arguing.
- thin slice
- thin layer
- thin wall
- thin ice
- paper thin
Grammar Patterns
thin + noun (attributive)
be + thin (predicative)
Usage Note
Gradable adjective: you can say thinner, thinnest, very thin, too thin.
Common Mistakes
2. having a body with very little fat or muscle so that the shape of the bones can
having a body with very little fat or muscle so that the shape of the bones can often be seen.
Heloísa was tall and thin, with long legs like a dancer.
predicative: be + thin describing a person
After the long illness, the old man's thin face showed every bone.
attributive: thin + body part (face)
Putri wrapped her thin arms around her knees in the hospital waiting room, staring at the floor.
The stray cat was dangerously thin, with its ribs clearly visible through its fur.
collocation: dangerously thin
- tall and thin
- long and thin
- thin face
- thin arms
- dangerously thin
Grammar Patterns
be + thin (describing body)
thin + noun (body part)
Usage Note
Can describe both positive slimness and concerning thinness depending on modifiers (e.g. 'pleasantly thin' vs 'dangerously thin').
Common Mistakes
3. reduced to a very thin state by continuous use, pressure, or the passage of time
reduced to a very thin state by continuous use, pressure, or the passage of time so that the material is weak or nearly gone.
The soles of Cyrus's shoes had worn thin after months of hiking on rocky trails.
pattern: wear + thin (become thin from use)
The knees of Minho's jeans became thin after two years of daily wear.
The old woollen blanket was so thin that light passed right through the faded fabric.
result of age and use
Hugo's favourite cotton shirt grew thin at the collar from years of washing.
- wear thin
- grow thin
- become thin
- worn thin
- threadbare
specifically for fabric or cloth that has worn thin
- worn
focuses on damage from use, not necessarily thinness
Grammar Patterns
wear + thin
grow + thin
become + thin
Usage Note
Often appears with verbs like 'wear' and 'grow' to describe gradual thinning from use or age. Distinguish from sense 1 (NOT THICK), which describes a permanent physical property; sense 3 describes a change over time.
4. so fine or delicate that light passes through or objects on the other side can b
so fine or delicate that light passes through or objects on the other side can be partly seen.
The curtains were so thin that sunlight filled the room every morning.
pattern: so thin that... (result clause)
Imran could see the outline of the tree through the thin paper of the envelope.
Tamar wore a thin silk scarf that seemed almost see-through in the bright light.
collocation: thin + fabric type (silk)
The thin cotton of his shirt showed the tattoo on his shoulder underneath.
- thin fabric
- thin material
- thin cloth
- thin paper
- thin silk
- sheer
technical term for very thin fabric you can see through
- translucent
formal; lets light through but not clear images
- transparent
you can see clearly through; stronger than thin
Grammar Patterns
thin + noun (fabric/material)
so thin that...
5. present in a smaller number or amount than usual or expected; not plentiful.
present in a smaller number or amount than usual or expected; not plentiful.
The audience was thin on the rainy Tuesday evening.
predicative: be + thin describing crowd size
Job openings were thin in the small village where Eli grew up.
Traffic on the highway was thin late at night, making the drive peaceful.
Padma noticed that the crowd was thin at the early morning yoga class.
collocation: thin crowd
- thin crowd
- thin attendance
- thin traffic
- thin on the ground
Grammar Patterns
be + thin (for amounts/crowds)
thin on the ground
Usage Note
Usually used predicatively (e.g. 'the crowd was thin'). Less common attributively (e.g. 'thin attendance'). Often describes people, traffic, opportunities, or evidence.
Common Mistakes
6. of air at high altitudes, where the amount of available oxygen is far lower than
of air at high altitudes, where the amount of available oxygen is far lower than what people are used to at sea level.
The air grew thin as the climbers approached the top of the mountain.
pattern: air + grow/become + thin (gradual change)
Hikers on the high plateau found the thin air made breathing difficult.
attributive: thin air
Christopher felt dizzy in the thin air of the high-altitude city.
Pilots receive special training for dealing with the effects of thin air.
- thin air
- air grows thin
- become thin (air)
Grammar Patterns
thin + air
the air is + thin
Usage Note
Almost exclusively used with the word 'air'. Not used for other gases or liquids in this sense.
Common Mistakes
7. Having a high proportion of water or another agent so that a liquid flows and po
Having a high proportion of water or another agent so that a liquid flows and pours easily rather than being thick or sticky — used of sauce, soup, paint, oil, and similar substances.
The sauce was too thin, so Chef Dario added cornstarch to thicken it.
opposite: thicken
After boiling, the soup becomes thin and watery, perfect for a light meal.
collocation: thin and watery
Saira prefers her paint thin so it spreads smoothly across the canvas.
A thin oil flows through the engine faster than a thick one.
The medicine is a thin liquid that you drink from a small plastic spoon.
- thin liquid
- thin sauce
- thin soup
- thin paint
- thin oil
- thin and watery
- too thin
Usage Note
Frequently paired with thick as an antonym pair; the opposite of thinning a liquid is thickening it.
Common Mistakes
8. Lacking strength, substance, or quality — used when a sound does not sound full,
Lacking strength, substance, or quality — used when a sound does not sound full, an excuse or argument is not convincing, support is not sincere, or something is of poor overall quality.
Christopher offered a thin excuse for being late — a stray goat had blocked his driveway — and no one believed him.
collocation: thin excuse = unconvincing
Aoi's voice sounded thin and shaky during the outdoor concert, barely reaching the audience in the back rows.
collocation: thin voice = weak, lacking fullness
The film's plot was too thin to hold the audience for two hours.
collocation: thin plot = lacking depth or detail
Yael gave a thin smile when she heard the news, hiding her true feelings.
collocation: thin smile = not sincere or enthusiastic
Rachid's argument was so thin that the judge dismissed it immediately.
- thin excuse
- thin voice
- thin smile
- thin plot
- thin argument
- thin material
- thin support
- strong
direct opposite across all contexts
- convincing
specific to arguments and excuses
- rich
for sounds, voices, or materials that are full and resonant
Usage Note
Most commonly used with nouns like excuse, voice, smile, argument, plot, and material. The meaning varies slightly by noun: thin excuse = easy to disprove; thin voice = high and lacking resonance; thin smile = forced or insincere.
Common Mistakes
9. Growing or arranged with wide gaps between individual items rather than being pa
Growing or arranged with wide gaps between individual items rather than being packed close together — used of hair, fur, grass, or other vegetation where the focus is on density of physical distribution.
Min's hair is naturally thin, so she uses special products to add volume.
collocation: thin hair = not dense
The grass on the hillside was thin, with patches of bare soil showing through.
Tunde planted lavender in the thin spots of his garden, hoping the poor soil would finally grow something.
The trees at the forest's edge are thin and let sunlight reach the ground.
collocation: thin trees = spaced far apart
The vegetation on the mountain top is thin because the wind is too strong.
- thin hair
- thin grass
- thin vegetation
- thin trees
- thin forest
- thin crop
Usage Note
Commonly describes hair, fur, grass, crops, trees, or other vegetation. The focus is on density of distribution rather than total quantity. Distinguish from adj/1 (physical thinness of an object) and adj/5 (a small number of people or things in a space).
To be in a risky situation where something bad could happen.
Maya knew she was skating on thin ice by lying to her boss.
Are you walking on thin ice by investing all your savings in that startup?
To disappear completely and suddenly, often in a way that seems impossible.
The magician made the rabbit vanish into thin air.
My keys disappeared into thin air; I searched everywhere.
To experience many problems or difficulties and not be successful.
The small business had a thin time of it during the recession.
Did you have a thin time of it after the accident?
out of thin air
idiomAppearing suddenly from nowhere, as if by magic.
The chef created a delicious meal out of thin air.
Can you conjure up a solution out of thin air?
To try to do too many things at once, so you do none of them well.
Diego spread himself too thin by joining three clubs.
Are you spreading yourself too thin with all these projects?
If things or people are thick on the ground, there are many; if thin, there are few.
Good restaurants are thin on the ground in this small town.
During the festival, tourists were thick on the ground.
A small action or event that is the start of something much worse.
The new fee is the thin end of the wedge for library services.
Many see the ban as the thin end of the wedge for free speech.
thin/bald on top
idiomHaving little or no hair on the head.
My uncle is getting thin on top at age forty.
Is your grandfather bald on top?
a thin skin
idiomThe inability to accept criticism or offensive remarks without getting upset.
Sara has a thin skin; she cries at any negative feedback.
You need a thick skin, not a thin skin, to be a comedian.
In all situations, even when there are problems or difficulties.
Aiden has supported his friend through thick and thin.
They stayed together through thick and thin for fifty years.
To be in a difficult situation where you must be very careful not to make a mistake.
The comedian walked a fine line between humor and offense.
She treads a thin line between confidence and arrogance.
wear thin
idiomTo become weaker, less effective, or less acceptable over time.
My patience with the noise is wearing thin.
His excuses are wearing thin after so many lies.
thin — adverb
1. with very little thickness between two opposite surfaces; in a way that leaves s
with very little thickness between two opposite surfaces; in a way that leaves space between individual people or things
Marta sliced the cucumber thin for the salad she brought to the party.
verb + thin (adverb of result)
The morning fog lay thin over the valley near Lucía's village.
Cyrus spread the butter thin on his toast to save some for later.
spread + thin (adverb of manner)
Scattered thin across the wide lawn, the autumn leaves looked like gold.
passive + scattered thin (sparse distribution)
Eri cut the sourdough bread thin for the cheese board she prepared.
- cut thin
- slice thin
- spread thin
- scatter thin
- lay thin
- thickly
opposite for both thickness and density
Grammar Patterns
cut/slice/spread/scatter + thin
Usage Note
Thin as an adverb appears most often after verbs describing cutting, spreading, or distributing. In more formal writing, 'thinly' is preferred; 'thin' sounds more natural in everyday speech and recipes.
Common Mistakes
Word family
- thinlyadverbB1
- thinnessnounB2
- thinnernounB1
- thinly disguisedadjective phraseB2
Synonym discussion
Sense: adjective/2
All five words describe a body with little fat, but each carries a different tone. Thin is the most neutral and general — it describes the physical fact ("a thin man") without necessarily judging it, though context matters. Slim is almost always positive: it suggests an attractive, well-proportioned thinness, often the result of fitness ("she keeps slim by swimming"). Slender is more delicate and elegant than slim, suggesting long and graceful lines ("a slender young woman with delicate hands"). Skinny is informal and often negative: it suggests someone is too thin, possibly unhealthily so ("he looked skinny after the illness"). Lean is positive in a different way: it describes a body that is thin but firm, with visible muscle ("the lean figure of a long-distance runner"). Use slim or slender for compliments, lean for athletic builds, thin for neutral description, and skinny only when you mean "too thin".
Common collocations
Adverbs
- extremely thin
- dangerously thin
- noticeably thin
- unusually thin
Phrases
- thin on the ground
- wear thin
- spread (oneself) thin
- appear / come out of thin air
- thin as a rake
- paper-thin
- the thin end of the wedge
- a thin line between (two things)
- into thin air
Prepositions
- thin with (diluted by)
- thin on (scarce in a place)
Etymology
Thin traces back to Old English þynne, meaning "thin, slender, not thick". It comes from Proto-Germanic *þunnuz, which is related to German dünn and Dutch dun. All of these go back to an ancient Indo-European root *ténh₂us, meaning "stretched out, thin", which also gave Latin tenuis (thin, fine) — the source of English words like tenuous and attenuate. The basic physical meaning (adj/1 NOT THICK) is the oldest; the figurative senses (weak, scarce, transparent) developed in Middle English as extensions of the original idea of something being stretched so far that it becomes less in some quality.