The two-word stage
Depending on what we count as an occurrence of two distinct words used together,
the two-word stage can begin around eighteen to twenty months, as the child’s vocabulary moves beyond fifty words. By the time the child is two years old, a variety of combinations, similar to baby chair, mommy eat, cat bad, will usually have appeared. The adult interpretation of such combinations is, of course, very much tied to the context of their utterance. The phrase baby chair may be taken as an expression of possession (= this is baby’s chair), or as a request (= put baby in chair), or as a statement (= baby is in the chair), depending on different circumstances.