which one do they know more words in? Which one did they pick up words faster in?

DH speaks to DS (16 months) in Chinese. He hears English from everyone else. I'm really surprised how many Chinese words he's picking up seeing as he only hears it from DH.

I'm wondering if some of the Chinese words are easier for him than the English version so he picks whatever is easier for him to say. Like he will only call the dog "go go" but he knows what dog means when I say it in English. And yesterday we were reading a book and there was a picture of a cat. I said to him "cat" and pointed at it. DH was in the room and said "mao mi" He only attempted to say "mao mi".