Adult and adolescent come from the same root word.
Adulting was the Grammar Girl word of the year last year—adulting, a verb that was newly invented from the noun adult. Today, we’ll complete the circle, and talk about how the noun adult itself came from another verb.
Going by the Oxford English Dictionary and John Traupman’s New College Latin & English Dictionary, our word adult comes from the Latin verb adolescere. Now when you hear that you might be thinking, “Hey, that sounds more like the word adolescent than the word adult!” Well, you’re right: adolescent and adult both come from that same verb. Its Latin meaning is “to grow up.” The noun and adjective adolescent come from the present participle adolescens, which in English would be the –ing form of the verb: “growing up.”
But where did that –esce- suffix disappear to in the word adult? That has to do with another Latin verb, the one that adolescere was derived from. That verb is adolēre, which also means “to grow up.” Our word adult comes from adultum, the past participle of adolēre. In other words, adult literally means “grown up” in Latin. So if you think calling adults “grown-ups” sounds childish, take note: That’s what Latin speakers did, too.
So if I just got through saying that our word adult came from the Latin adolēre, why did I say earlier that it and adolescent both came from the Latin adolescere? The verb adolescere is what’s known as an inchoative or inceptive verb. The –esce- suffix turns the meaning from just “grow up” to “begin to grow up,” which is what adolescents are doing—at least some of them. But Latin speakers didn’t bother creating a new past participle for adolescere; they just kept using adultum, the past participle from the verb adolēre.
However, the funniest thing about the etymology of adolescent is that there’s actually another verb in Latin, a homonym for adolescere, which means “to begin to smell bad.” So although I haven’t found this etymology in the dictionaries, you could argue that the word adolescent is derived from a word that meant “beginning to smell bad,” which is certainly appropriate, don’t you think?
Finally, while we’re on the subject of suffixes and the word adult, it’s ironic that while adult and adolescent do come from the same root, adult and adultery don’t! Although they both contain the Latin prefix ad-, the word adultery ultimately traces back to the Latin adjective alter, meaning “other.”
That segment was written by Neal Whitman, who has a PhD linguistics and blogs at literalminded.wordpress.com.