Fifteen is the number equal to ten plus five. It comes right after fourteen and before sixteen.
It comes from Old English “fīftēne,” formed from “fīf” (five) and “tēne” (teen, meaning “ten more than”). The “-teen” ending is the same one used in other teen numbers.
The “-teen” in “fifteen” literally signals “and ten,” like a built-in math formula. Many languages build numbers this way, turning counting into a tiny story hidden in the word.
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