The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe ( ' ) or single closing quotation mark in many typefaces, but it differs from them in being placed on the baseline of the text. Some typefaces render it as a small line, slightly curved or straight but inclined from the vertical, or with the appearance of a small, filled-in.
The comma is used in many contexts and languages, mainly for separating parts of a sentence such as clauses, and items in lists, particularly when there are three or more items listed. The word comma comes from the Greek, which originally meant a cut-off piece; specifically, in grammar, a short clause.