Pronunciation: (kom'u),[key] —n. 1. the sign (,), a mark of punctuation used for indicating a division in a sentence, as in setting off a word, phrase, or clause, esp. when such a division is accompanied by a slight pause or is to be noted in order to give order to the sequential elements of the sentence. It is also used to separate items in a list, to mark off thousands in numerals, to separate types or levels of information in bibliographic and other data, and, in Europe, as a decimal point.
2. Class. Pros. a. a fragment or smaller section of a colon.
b. the part of dactylic hexameter beginning or ending with the caesura.
c. the caesura itself.
3. Music.the minute, virtually unheard difference in pitch between two enharmonic tones, as G♯ and A♭.
4. any of several nymphalid butterflies, as Polygonia comma, having a comma-shaped silver mark on the underside of each hind wing.