At 2 years of age, the child can combine words, forming simple sentences like "Daddy go."

At 3 years of age, the child can use sentences two- to four-words long, follow simple instructions, and often repeat words he/she overhears in conversations.

At 4 years of age, the child can understand most sentences, understands physical relationships (on, in, under), uses sentences that are four- or five-words long, can say his/her name, age, and sex, and uses pronouns. Strangers can understand the child’s spoken language.