ボタンが１つとれましたよ。

ボタンが１つとれましたよ。

One of your buttons has come off.

ボタンが１つとれましたよ。

Botan ga hitotsu toremashita yo.

牡丹 (ぼたん、ボタン)

tree peony (Paeonia suffruticosa); moutan; wild boar (meat)

が (が)

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

一つ (ひとつ)

one; for one thing; only; (not) even; just (e.g. "just try it")

獲れる (とれる)

to be harvested; to be reaped; to be yielded; to be able to harvest; to be able to reap; to be able to yield

よ (よ)

indicates certainty, emphasis, contempt, request, etc.; used when calling out to someone; used to catch one's breath or get someone's attention; yo!