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 figure 9.
The comma is used in many contexts and languages, mainly to separate 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 κόμμα (kómma), which originally meant a cut-off piece; specifically, in grammar, a short clause.
A comma-shaped mark is used as a diacritic in several writing systems, and is considered distinct from the cedilla. The rough and smooth breathings (ἁ, ἀ) appear above the letter in Ancient Greek, and the comma diacritic appears below the letter in Latvian, Romanian, and Livonian.