noun

• (typography) The punctuation mark ⟨,⟩ used to indicate a set of parts of a sentence or between elements of a list.
  "No points were used by the ancient printers, excepting the colon and the period; but, after some time, a short oblique stroke, called a virgil, was introduced, which answered to the modern comma. In the fifteenth century this punctuation was improved by the famous Aldus Manutius with the typographical art in general; when he gave a better shape to the comma, added the semicolon, and assigned to the former points more proper places."
• (Romanian typography) A similar-looking subscript diacritical mark.
• (entomology) Any of various nymphalid butterflies of the genus Polygonia, having a comma-shaped white mark on the underwings, especially Polygonia c-album and Polygonia c-aureum of North Africa, Europe, and Asia.
  "Commas (Polygonia comma) and Question Marks (Polygonia interrogationis) occur from the Gulf Coast to Canada and west to the Rockies. [...] Question Marks and Commas are handsome butterflies with burnt orange and black markings. [...] On the underside of each hind wing of the Comma is a small, distinctive silver hook that resembles a comma."
• (music) A difference in the calculation of nearly identical intervals by different ways.

verb

• (rare, transitive) To place a comma or commas within text; to follow, precede, or surround a portion of text with commas.