Depending on what we count as an oc

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