Im not sure how many words warrant an actual sentence but i voted 17-18mths - Elody started stringing two words together a little earlier though (bye mummy, thats mine, come here etc) and three worded sentences she started at about 17 and a half mths (it her baby, thats my dog) she says two words together a lot but three words are only occasional atm :)
Thanks guys... I thought my first started talking early, but my 11 m old has said 4 word sentences already. I just wondered if she's unusual or an "early talker". The Dr. said it wasn't unheard of and laughed about it (she talked to him) at our last check-up, but didn't act shocked or anything. Wish I had more poll results to see how odd this really is...