underline

underline — verb

1. to write a straight line underneath a word, phrase, or sentence so that it stand

1.verbtransitiveB1
Definition

to write a straight line underneath a word, phrase, or sentence so that it stands out from the rest of the text.

Example

Yael underlined the key dates in her notebook so she would not miss them.

underline + noun phrase for emphasis in notes

The teacher told the class to underline every verb in the short story.

Common collocations
  • underline + word / phrase / sentence / title
  • underline + in red / in pencil
  • underline + with a pen / with a ruler
Synonyms
  • underscore

    more formal or technical; common in computing (e.g., underscore character _)

  • mark

    broader meaning — can mean any kind of written sign, not just a line underneath

  • highlight

    can mean using a bright marker pen to cover text, not just drawing a line

Grammar Patterns

underline + noun phrase

Usage Note

Common in note-taking, studying, and proofreading. The passive form — e.g., 'the word was underlined in red' — is also frequent.

Common Mistakes

I underlined the text with a yellow highlighter.
I highlighted the text with a yellow marker.
Underlining means drawing a line under the text, not covering it with colour.

2. to call strong attention to a fact, idea, or need by stating it clearly or by gi

2.verbtransitiveB2
Definition

to call strong attention to a fact, idea, or need by stating it clearly or by giving it special weight in what you do.

Example

The government report underlines the need for more affordable housing in cities.

underline + noun phrase (abstract object: need/importance)

Dario underlined that even small donations can make a real difference to the charity.

underline + that-clause

Common collocations
  • underline + the importance / the need / the danger / the significance
  • underline + that-clause
  • underline + how / what / why
Synonyms
  • emphasize

    more general and slightly more formal; used in both speech and writing

  • stress

    suggests giving extra force or repeating something so it is not missed

  • highlight

    focuses on making something stand out so that people notice it

Antonyms
  • downplay

    to make something seem less important than it really is

  • minimize

    to reduce the perceived importance or seriousness of something

Grammar Patterns

underline + noun phrase

underline + that-clause

Usage Note

The object is often an abstract noun such as 'importance', 'need', 'danger', or 'significance'. This sense also commonly takes a that-clause or a wh-clause. Compare with sense 1 (DRAW LINE UNDER), which is always literal.

Common Mistakes

He underlined the importance about regular exercise.
He underlined the importance of regular exercise.
The noun after 'underline' takes 'of', not 'about'.

underline — noun

Word family

  • underlining
    nounB2
  • underlined
    adjectiveB2

Synonym discussion

Sense: verb/1

All three words involve making text more noticeable, but they differ in method and context. 'Underline' means drawing a physical line beneath the text — a concrete action common in handwritten notes and proofreading. 'Underscore' is more formal and also refers to the underscore character (_) used in computing and typing. 'Highlight' can mean either marking text with a bright marker pen (covering the text itself, not just the line beneath) or drawing attention to something figuratively. In academic writing, 'underline' is the everyday word for the literal action; 'underscore' is rarer and more technical. For figurative emphasis (verb/2), all three overlap, but 'underline' is less formal than 'underscore' and more direct than 'highlight'. Example: 'Please underline the topic sentence in each paragraph.' vs. 'The editor highlighted the key phrases with a yellow marker.'

underline ↗underscorehighlight ↗

Common collocations

Nouns

Adverbs

Phrases

  • underline the fact that
  • underline the importance of
  • underline the need for

Prepositions

Etymology

Old EnglishMiddle EnglishEnglish

The word 'underline' was formed in Middle English by combining the prefix 'under-' (meaning below or beneath) with the noun 'line'. It first appeared around the 15th century as a verb meaning to draw a line beneath text. The figurative sense (to emphasize) developed later, by the 18th century, as a natural extension of the idea that marking something with a line signals its importance. The noun form, referring to the line itself, came into use in the 19th century.