Comma the purpose of the comma. There are also a number of comma-like diacritics with "COMMA" in their Unicode names. These do not serve a punctuation function. A comma-like low quotation mark is also available (shown below; raised single quotation marks are not shown). Various other Unicode characters combine commas or comma-like figures with other characters, and are not shown here. In the 3rd century BC, Aristophanes of Byzantium invented a system of single dots ("distinctiones") that separated verses (colometry) and indicated the amount of breath needed to complete each fragment of the text when reading aloud. The different lengths were
Colon (punctuation) Colon (punctuation) The colon ( : ) is a punctuation mark consisting of two equally sized dots centered on the same vertical line. A colon precedes an explanation or an enumeration, or list. A colon is also used with ratios, titles and subtitles of books, city and publisher in bibliographies, Biblical citations between chapter and verse, and for salutations business letters and other formal letter writing, and often to separate hours and minutes. The most common use of the colon is to inform the reader that what follows the colon proves, explains, defines, describes, or lists elements of what preceded