flower, I didn't respond about what constitutes a large vocabulary at 18 months since I'm not sure what a pediatrician or a speech pathologist would look for, but I can assure you without a shadow of a doubt that 100 words at 16 months (even if some are signed and not spoken) and over 300 spoken words at 18 months definitely fits the definition of a large vocabulary! And, I'm virtually certain that for a word to "count" it doesn't have to be said perfectly clearly -- just consistently or clearly used to mean a particular thing. HTH!
