"Se acabó mi diente"?
I work with a few kids who are bilingual or speak Spanish as their first language. The other day, one of them had a tooth fall out. He said something like "se acabó mi diente!", a phrase which I haven't been able to find in the dictionary. Does this mean "I lost a tooth" or something similar? Or did I hear it wrong? How do you say that if it is incorrect?
(Also, I didn't know which category to put this in so I apologize if it's in the wrong one.)
7 Answers
I'd say it probably is "se cayó mi diente" - my tooth fell down. Not the way I would say it. Polenta's version is a lot better, but won't surprise me coming from a kid.
Se me cayó el diente
You heard correctly and spelled it perfectly, including the accent on acabó.
se acabó means something is done / finished.
It comes from the verb acabarse. Se acabó is in the 3rd person, singular (the tooth / it) of the preterite. - a specific and/or sudden event. In this case, the fact that it is done/over and this finishing was completed at a specific time makes the preterite the past tense of choice.
In English, one might say: My tooth is done for. (it is no more, it's gone, I'm done with it, etc.)
Here is a portion of the dictionary entry which will show you some common ways that se acabó can be used.
acabarse
PRONOMINAL VERB
4. (to be used up)
a. to run out
Se acabó la leche y no puedo hacer mi café mañanero.
The milk has run out and I can't make my morning coffee.
5. (to run its course)
a. to end
Siguieron bailando aun después de que se acabara la música.
They kept dancing even after the music ended.
b. to finish
La película se acabó temprano. The movie finished early.
As you can see see from the example sentences, using se acabó in this way (the tooth) is perfectly understandable. It means something is over or "has run out". I would say it is more often used with an event, a party, the music, a movie or with something that runs out...milk, bread, gasoline, etc. However, using is with a body part that is "finished" seems fine to me. I am not a native speaker, so you may want to wait for other opinions.
In terms of another way of saying it, how about:
Se me rompió el diente. - My tooth broke - Literally: The tooth broke on me.
Se me cayó el diente. - My tooth fell out - Literally - The tooth fell out on me.
Using these structures with me as an indirect pronoun - the person effected , and a definitive article (el / the) instead of a possessive article ( mi / my) is more typical Spanish, but there is nothing wrong with using the possessive mi here.
It sounds weird. I would have have said it lke: Se me cayo el diente.
"se acabó mi diente!",
Hi Heroina, welcome to the forum.
Very nice post, correct category and all, thanks for taking the time to be so careful. 
Do you think the kid might have said:
se acabó de caer mi diente
o
se me acabo de caer el diente.
In any case, se acabó mi diente, even though odd (but after all we are talking about kids here) is understandable.
It would be like saying: my tooth is finished...well, we would probably also understand, even though it sounds odd.
My listening skills aren't the best so I only catch a few words here and there so that's probably what he said. I did get all excited though thinking I had understood something. - LaHeroína
Well, you got excited for a good reason, you DID understand 
I agree with some members who suggested
"se me cayó el diente"....which sounds more or less what you thought he said.
Or simply : se cayó el diente....as he was pointing at it.
I would say, "My tooth is a 'goner'".
