1 year to 1 1/2 years--Identification Language
Actually, the receptive vocabulary of the one year old child will probably be much larger than 50 words, if you have been reading to him/her every day, and talking to the child a lot.
It is a thrill at 10 and 11 months to tell the ãspeechless little speck of humanityä we call our baby to get daddy's shoe and have him/her actually do it.
This first word that the child utters may not be a perfect pronunciation. It may be, for example, "dada" for "father" or "baba" for "bottle." But the consistency with which he/she uses the word in the presence of the object (referent) leaves no doubt as to its meaning.
Sometimes the word is a composite, like "bye-bye-now." Although to the adult, it may seem like two words, to the child it is all one. If this were a 400 level course, we would call this a progressive phonological idiom.
The vocabulary will grow slowly from this point on.
NOTES: Here are some more milestones related to hearing.
NOTES: And if you didn't have enought milestones already, here's a few more.