What does underline mean?
Underline means to draw a line beneath text, usually to show that a word, phrase, or passage deserves attention. The word can also be used more broadly to mean emphasize, highlight, or make an important point especially clear, as in “the report underlines the need for reform.” In writing and publishing, underlining is a familiar visual technique, while in speech and abstract discussion it functions as a metaphor for drawing attention. The expression has a neutral, straightforward tone but can suggest deliberate emphasis or, occasionally, excessive attention to a detail. As a noun, an underline is the line itself, and the related form “underlining” can describe the practice or the resulting emphasis. Across both literal and figurative uses, the word centers on visibility and importance: it identifies what readers should notice before moving on.
To draw a line beneath a word or passage, especially to indicate emphasis or attention; to emphasize or highlight an idea.
"He underlined the date and wrote a note beside it."
The figurative sense is common in formal discussion: “the evidence underlines the importance of…”
A line drawn beneath text as a mark of emphasis or attention; the act of underlining or emphasizing something.
"The underlined terms indicate the main vocabulary from the lesson."
The singular noun “an underline” is less common than the gerund “underlining” when referring to the practice generally.
The plural is used when referring to multiple lines placed beneath separate words or passages.
"The editor placed several underlines beneath key phrases."
From a literal line beneath a word to a universal sign of emphasis: underline has made attention visible for centuries.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does underline come from?
“Underline” was formed in English from the preposition “under” and the noun “line,” with the meaning of drawing a line beneath text. The compound reflects the literal arrangement conveyed by its components: something is marked by placing a line below it. Its “line” element ultimately derives from Latin “linea,” meaning a straight line, through Old French and English.
Related word forms
How underline is actually used
The verb is common in both formal and informal contexts. When used figuratively, it often suggests that something is being made especially prominent or treated as important. As a noun, “underline” is less common in everyday use than the related gerund “underlining,” especially in digital and typographic contexts.
Easily confused with underline
Underline means to emphasize text by drawing a line beneath it or otherwise drawing attention to it, whereas underlying means existing beneath something or forming its basis.