underline
UK: ˌʌn.dəˈlaɪn | US: ˌʌn.dɚˈlaɪn
vt. to draw a line beneath a word or phrase for emphasis or annotation
n. a line drawn under text, typically to indicate importance or to mark for editing
The word "underline" combines "under" (from Old English under, meaning "beneath") and "line" (from Latin linea, meaning "string, mark"). It emerged in Middle English (16th century) as a verb describing the act of marking text from beneath, later nominalizing to refer to the mark itself. The morphemes retain their original meanings, reflecting the straightforward logic of "a mark below."
Please underline the key terms in this paragraph.
The editor added an underline to highlight the error.
Students often underline important dates in their textbooks.
The contract requires you to underline your signature.
Digital tools allow you to underline text with a single click.