It is so different by child. We have a friend whose daughter (I can tell she is smart now -2yrs) didn't utter a word until 18 mo, she is just now (26mo) putting two words together but her vocab is growing dramatically by day. My nephew was crazy old, I was convinced he had autism, but then he started speaking in complete sentences and seems bright.
DD on the other hand was using 25 words on a regular basis by 1 and had a crazy "vocab" of different animal sounds (over 25). She was also saying "all done" as she signed it. I didn't realize she was speaking early until at our 9 month apt Apt the doctor said I can't believe she is talking. I haven't ever ever had a baby who could talk by 9 mo. (she was saying "up", "agua", "mom", "dad", and "miu" (for milk). It didn't seem like a ton to me but apparently he thought it was.
I have read about several children on this board not talking until later then talking in sentences. Also, wasn't it Einstein that didn't talk until he was 3? Apparently his mom thought he was mentally challenged or something. Different for every child. The very early talkers do seem to be very smart, but that doesn't mean late talkers will not be.
