What does underlining mean?
Underlining is the practice of drawing a line beneath words or other text to make them stand out, call attention to them, or show that they are important. It can refer to the action itself, as in “the underlining of key passages,” or function as a gerund in phrases such as “underlining titles in a document.” The technique is common in printed materials, study notes, proofreading, and older conventions of emphasis, where it offers a direct visual alternative to changes in typeface or color. In everyday use, underlining can suggest careful attention, annotation, or a schoolbook habit of marking significant information. It remains common in formal documents and instructional materials, although digital design has favored bold text, italics, color, and highlighting. Underlining is especially useful when a clear, universally recognizable mark is needed without changing the words themselves.
The action or practice of drawing a line beneath text in order to emphasize it, mark it, or direct attention to it.
"The underlining in the manuscript indicates passages that the editor considered significant."
Usually used as an uncountable noun; the plural is uncommon.
As the present participle or gerund of underline, meaning to draw a line beneath text in order to emphasize or mark it.
"The publisher is underlining the title of every new release."
In this form, underlining can function as a gerund (“the underlining of text”) or as a present participle in an ongoing action (“she is underlining the headings”).
The plural is uncommon; underlining is normally used as an uncountable noun.
"The archive preserves the editor's underlinings on several pages."
Underlining is typography's classic visual shout: a simple line that tells readers where to look.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does underlining come from?
Underlining is formed from the English verb underline, with the suffix -ing. The compound combines the prefix under-, meaning beneath, with line, a word that ultimately derives from Latin linea, meaning a row, line, or written line. The practice of placing a line beneath text developed from the older English verb underline, whose sense developed from marking or drawing a line below a word to make it noticeable. Related English words such as interline and interlinear also trace their names to the Latin root linea.
How underlining is actually used
In contemporary digital communication, underlining is less common than boldface, italics, or highlighting. In traditional print and in formal editing, it can be a neutral way to mark emphasis, though excessive underlining may make a document look informal or difficult to read.
Easily confused with underlining
Underlining is the visual act of marking text with a line below it, whereas underlying means fundamental or lying beneath the surface.
Underlining draws attention with a line beneath text, while outlining identifies or briefly describes the main points of something.