expression

expression — noun

1. The act of communicating your thoughts, feelings, or opinions through speech, wr

1.nounB1
Definition

The act of communicating your thoughts, feelings, or opinions through speech, writing, art, or other actions — for example, a poem that reveals a writer's grief, or a public march that shows people's anger about a new policy.

Example

The teacher encouraged Min to find a creative expression for his ideas during art class.

find + adjective + expression for

Kwame believes that freedom of expression is essential for a healthy society.

freedom of expression (fixed phrase)

Common collocations
  • freedom of expression
  • give expression to
  • find expression in
  • form of expression
  • expression of [gratitude/anger/joy]
Synonyms
  • communication

    broader term covering all information exchange, not just personal feelings

  • utterance

    more formal and limited to spoken or written words

  • manifestation

    more formal; implies an outward sign of something abstract

Antonyms
  • suppression

    the act of preventing thoughts or feelings from being shown

Grammar Patterns

expression of [emotion/opinion]

find [adjective] expression in [medium]

freedom of expression

Usage Note

The uncountable form (expression) refers to the general ability or act — 'freedom of expression.' The countable form with 'an expression of' points to a specific instance — 'an expression of gratitude.' In formal writing, 'give expression to' can replace 'express' for a more literary tone.

Common Mistakes

The freedom of expression is important.
Freedom of expression is important.
No article is used before this fixed phrase.
I need to find a expression for my feelings.
I need to find an expression for my feelings.
'Expression' begins with a vowel sound, so it takes 'an.'

2. The way someone's facial features appear when they are experiencing a particular

2.nounA2
Definition

The way someone's facial features appear when they are experiencing a particular emotion — a broad grin when delighted, or a furrowed brow when confused.

Example

Elena's expression changed from confusion to understanding when she heard the answer.

expression changed from [emotion] to [emotion]

Rachel could tell from her father's expression that the news had upset him deeply.

tell from + possessive + expression

Common collocations
  • facial expression
  • blank expression
  • worried expression
  • neutral expression
  • expression on [someone's] face
Synonyms
  • look

    less formal and broader than 'expression'; can also refer to appearance in general

  • face

    informal, as in 'make a face at someone'

  • countenance

    very formal and literary; refers to the whole facial appearance

Antonyms

Grammar Patterns

[possessive] + expression

expression + [preposition phrase]

Usage Note

When 'expression' refers to a facial look, it is almost always modified by an adjective describing the emotion (a worried expression, a blank expression). The phrase 'facial expression' is more explicit when the context could otherwise suggest sense 1.

Common Mistakes

His face had no expressions.
His face had no expression.
When referring to the general state of the face, 'expression' is uncountable.

3. A set phrase or specific combination of words that speakers use in a given situa

3.nounB1
Definition

A set phrase or specific combination of words that speakers use in a given situation or that belongs to a particular community — for instance, 'break a leg' in theatre circles, or 'bless you' after someone sneezes.

Example

Christopher learned a formal expression to use when writing letters to the university office.

formal expression

The expression 'break a leg' is a strange way to wish actors luck before a show.

the expression '[phrase]'

Common collocations
  • common expression
  • formal expression
  • informal expression
  • idiomatic expression
  • old-fashioned expression
  • local expression
Synonyms
  • phrase

    a group of words without a full verb; narrower and more technical than 'expression'

  • saying

    a well-known fixed expression that offers advice or wisdom

  • term

    a single word or short phrase with a specific meaning in a field

Grammar Patterns

the expression '[phrase]'

expression + for/in [language/context]

Usage Note

Distinguish from sense 1: this sense refers to the word or phrase itself as a unit of language, not to the act of communicating. In dictionaries, 'expression' often appears in usage labels such as 'fixed expression,' 'idiomatic expression,' or 'colloquial expression.'

Common Mistakes

That is just a expression people use.
That is just an expression people use.
'Expression' takes 'an' before it, not 'a.'
A phrase is the same as a expression.
A phrase is the same as an expression.
Same article rule.

4. In mathematics, a meaningful arrangement of numbers, letters, and operation symb

4.nounB2
Definition

In mathematics, a meaningful arrangement of numbers, letters, and operation symbols (such as +, −, ×, ÷) that stands for a single numerical value — for example, '3x + 5' or '(a + b)²'.

Example

The teacher asked Sora to simplify the algebraic expression on the whiteboard at the front.

algebraic expression

An expression such as '3x + 5' contains both a variable and a constant number.

expression such as [example]

Common collocations
  • algebraic expression
  • mathematical expression
  • simplify an expression
  • evaluate an expression
  • numeric expression
Synonyms
  • formula

    an expression that describes a general relationship; may contain an equals sign

  • equation

    two expressions joined by an equals sign — distinct from a single expression

Grammar Patterns

[adjective] + expression

expression + for [quantity]

Usage Note

In mathematics, an expression does NOT contain an equals sign — that would make it an equation. You can simplify or evaluate an expression, but you 'solve' an equation. Common in algebra, calculus, and computer programming contexts.

Common Mistakes

Solve the expression 3x + 5.
Simplify the expression 3x + 5.
You solve equations (which contain an equals sign), not expressions.
The expression 2 + 2 = 4.
The equation 2 + 2 = 4.
When there is an equals sign, it is called an equation, not an expression.

5. In biology, the process by which information stored in a gene is converted into

5.nounC1
Definition

In biology, the process by which information stored in a gene is converted into a visible or measurable effect in a living organism — for example, the way a gene tells cells to produce a particular pigment, resulting in brown eyes instead of blue.

Example

The research team studied gene expression in plant cells exposed to extreme temperatures.

gene expression

Scientists found that diet affects the expression of genes related to long-term heart health.

expression of [a specific group of genes]

Common collocations
  • gene expression
  • protein expression
  • expression level
  • expression of [a gene]
  • abnormal expression
  • gene expression pattern
Synonyms
Antonyms
  • gene silencing

    the process by which a gene is prevented from being expressed

Grammar Patterns

[gene/protein] expression

expression of [gene]

Usage Note

This technical sense belongs primarily to molecular biology and genetics. Learners are most likely to encounter it in university-level science reading. 'Gene expression' is the most common fixed pairing — the word 'expression' alone may be ambiguous outside a biology context.

Common Mistakes

The gene expressed the trait.' (confusing levels)
The gene was expressed, producing the trait.
Genes are not agents; they are expressed through cellular processes.

Word family

Synonym discussion

Sense: noun/3

All five words name units of language, but they differ in scope and fixity. 'Expression' is the broadest — any word or group of words used in a specific context, from 'hello' to 'raining cats and dogs.' 'Phrase' is a grammatical unit: a group of words that lacks a finite verb (e.g., 'under the table'). 'Saying' is a folk widsom formula — 'Actions speak louder than words' is a saying, not just an expression. 'Term' is a single word or short phrase with a precise meaning inside a field (e.g., 'mitosis' in biology). 'Idiom' is a fixed expression whose meaning cannot be guessed from the individual words — 'kick the bucket' means 'die,' not literally kick anything. In everyday use: 'pardon the expression' is the phrase you say after an awkward choice of words, whereas 'pardon the phrase' would sound odd.

expression ↗phrase ↗saying ↗termidiom

Common collocations

Nouns

Adverbs

Phrases

  • freedom of expression
  • beyond expression
  • pardon the expression
  • expression of interest

Prepositions

Etymology

LatinFrenchEnglish

The word 'expression' entered English in the 1400s through French, from Latin 'expressio' meaning 'a pressing out.' The Latin root 'exprimere' combined 'ex-' (out) and 'premere' (to press). Its earliest English use was physical — literally squeezing oil from olives. By the 1500s the meaning had shifted to 'putting thoughts into words,' as if pressing ideas out from inside the mind onto the page. The facial and mathematical senses developed later, in the 1600s and 1700s, while the genetic sense is a 20th-century scientific extension.