Comma (noun)

1. A punctuation mark (,) indicating a pause or separation in a sentence, or separating items in a list.
2. A punctuation mark used to indicate a pause or separation in a sentence, or to separate items in a list.

Origin:

From medieval latin comma, from ancient greek κόμμα (kómma, "clause, sentence"), from κεῖμαι (keîmai, "to lie, be at rest").

Examples:

1. Please use commas to separate items in a list.
2. The comma is used to separate items in a list.
3. The comma is used to separate the main clauses in a compound sentence.
4. The use of a comma can change the meaning of a sentence.
5. It is important to use commas correctly in writing.