TIL English teenager isn't necessarily the translation of Dutch tiener. Wikipedia at least says 10–19 for us and 13–19 for English. In German the word teenager is also used and the page gives both definitions on the same page without realising it's self-contradictory

Idk that anyone takes this so literally (as that you're only a teenager if your cardinal age ends in the literal word teen and so twelve is definitely not a teenager), I've always understood it as "in their tens" but that may be my origin