here’s a child’s turn from a conversation and a note about one aspect of the child’s vocabulary.
J (aged 2) said as he looked at and handled a toy plastic elephant:
A cow, ship, another cow.
1) What do you think J is trying to do?
2) Any guesses about the features of the toy that influenced his choice of label for it?
3) Think about a and another. J didn’t just say «Cow, sheep, cow». Think what this indicates about his knowledge of grammar and pragmatics.