How do I respond to what my child says so that he/she learns more language?

Use words that Answer

Words that answer are words that let your child know that you have heard what he/she said and that you understand their meaning. You are also giving your child the message that you are interested in what he/she said and that you want to talk more about it.

Repeat what the child just said:

Exactly
Child: "big train"
Parent: "big train!"

Partly
Child: "I ride bike"
Parent: "I ride too!"

Tell the child "yes, I hear you!":

Child: "Its a plane!"
Parent: "Yes, it is"