fog

fog — noun

1. a mass of tiny water drops that sits just above the ground and stops people from

1.nounA2
Definition

a mass of tiny water drops that sits just above the ground and stops people from seeing things that are far away.

Example

Thick fog covered the city, so drivers could barely see the road ahead.

collocation: thick fog / dense fog

The boat could not leave the harbour because of the heavy fog that morning.

Common collocations
  • thick fog
  • dense fog
  • heavy fog
  • patchy fog
  • fog lifts
  • fog clears
  • fog rolls in
  • fog bank
  • fog horn
  • fog lights
Synonyms
  • mist

    less thick than fog; you can still see through it fairly well

  • haze

    caused by dust or smoke, not water droplets; reduces clarity but not as severely as fog

Grammar Patterns

fog + verb (fog lifts/clears/rolls in)

a + adjective + fog (a thick fog, a dense fog)

Usage Note

Commonly used with adjectives like thick, dense, heavy, and patchy. The verb collocates fog lifts, fog clears, or fog rolls in describe changes in fog.

Common Mistakes

There was a fog in the sky this morning.
There was fog this morning.
fog is near the ground, not in the open sky.
The fog was very strong.
The fog was very thick / dense.
strong is used for wind, not for fog.

2. a condition of the mind where you feel confused, cannot think properly, or strug

2.nounB2
Definition

a condition of the mind where you feel confused, cannot think properly, or struggle to grasp what is going on around you.

Example

After the accident, Sayaka felt like she was walking around in a fog all day.

idiom: in a fog

The instructions used such difficult language that I was completely lost in a fog.

Common collocations
  • in a fog
  • a fog of confusion
  • a fog of exhaustion
  • a fog of grief
  • lost in a fog
Synonyms
  • daze

    suggests being stunned or shocked rather than just confused; often follows a physical hit or surprise

  • haze

    similar to fog but vaguer; a haze of fatigue implies less intense confusion than a fog

Antonyms
  • clarity

    clearness of thought, the opposite of being in a fog

Grammar Patterns

in a fog

a fog of + noun (a fog of exhaustion / confusion)

Usage Note

Almost always used in the phrase in a fog or a fog of [something]. The something is typically an abstract noun describing the cause of confusion (exhaustion, grief, worry).

Common Mistakes

I am fog.
I am in a fog.
the idiom requires the preposition in and an article a before fog.
His brain was full of fog.
His mind was in a fog.
the standard expression uses in a fog, not full of fog.

3. the uncertainty and lack of clear information that soldiers and leaders experien

3.nounC1
Definition

the uncertainty and lack of clear information that soldiers and leaders experience during a battle or war, making it hard to know what is actually happening.

Example

In the fog of war, commanders often make decisions based on incomplete information.

fixed phrase: fog of war

Historians still argue about what happened during the fog of that particular battle.

Common collocations
  • the fog of war
  • the fog of battle
  • the fog of conflict
  • lift the fog of war
Synonyms
  • uncertainty

    a general term; fog of war implies a military context with potentially dangerous consequences

  • chaos

    emphasises disorder rather than lack of information; broader in meaning

Grammar Patterns

the fog of war

the fog of + conflict-related noun

Usage Note

The phrase the fog of war is a fixed expression. It is used both in literal military contexts and metaphorically for any chaotic situation where facts are unclear.

Idioms

(in) a fog

idiom

in a mental state where you feel confused and unable to think or react clearly.

Erik had not slept all night and spent the whole meeting in a fog.

After hearing the bad news, Anong walked home in a fog, barely noticing the rain.

fog of war

idiom

the confusion and lack of clear information that exists during a military battle, often leading to mistakes or unexpected outcomes.

General Tendai knew that the fog of war made it impossible to predict the enemy's next move.

The documentary explored how the fog of war affected both soldiers and their families back home.

fog — verb

Word family

  • foggy
    adjectiveB1
  • fogged
    adjectiveB1
  • fogging
    nounB2
  • fogging
    adjectiveB2
  • fogginess
    nounC1

Synonym discussion

Sense: noun/1

Fog, mist, haze, and smog all describe conditions that reduce visibility, but they differ in composition, thickness, and context. Fog consists of tiny water droplets suspended near the ground and cuts visibility to under one kilometre — thick enough to disrupt travel. Mist is also made of water droplets but is less dense; you can still see objects a kilometre or more away, and it often burns off by mid-morning. Haze is not made of water at all — it comes from fine dry particles like dust, smoke, or pollution. It creates a bluish or greyish veil, reducing contrast without necessarily blocking sight. Smog (a blend of smoke and fog) is a thick, often yellowish or brownish haze caused by air pollution in cities, especially during temperature inversions. For everyday weather, fog and mist are natural, while haze and smog are linked to human activity or dry conditions. A weather report might say 'patchy fog early, then hazy sunshine' — the fog lifts, but the haze stays.

fog ↗mist ↗hazesmog ↗

Common collocations

Nouns

Adverbs

Phrases

  • in a fog
  • through a fog
  • peering into the fog
  • lost in the fog

Prepositions

Etymology

Old NorseDanishEnglish

The word fog entered English in the 1500s, most likely borrowed from Danish or Norwegian fog, meaning 'spray' or 'shower.' It may also be related to Old Norse fok, meaning 'drifting snow.' Before this word became common, English speakers used the word mist for all low-lying cloud conditions. Fog gradually took over the sense of 'thick, difficult-to-see-through mist' during the 1600s and 1700s.