the cardinal number that is the sum of twelve and one
"After counting all twelve apples on the table, I added one more to reach a total of thirteen fruits."
The cardinal number occurring after twelve and before fourteen, represented in Roman numerals as XIII and in Arabic numerals as 13.
"She was exactly thirteen years old when she received her first driving license."
Thirteen comes from Old English þrēotīene, which was formed by combining words for "three" and "teen." This structure reflects its origin in Proto-Germanic *þritehun.