When a child is learning how to speak they must learn the different components of language. Language is divided into three parts. Content, Form and Use.
Content
Content of language refers to the semantics of words or what words mean. This is the first component that is learned by a child. It includes vocabulary and it's associated object or action. A child can only really learn the word "car" by understanding that when they hear the sound waves that produces "car" it is a symbol for item itself. This is why the more concrete words (nouns) are usually learned first followed by actions (verbs) and finally the more abstract words (adjectives, adverbs, prepositions, etc.). So, the way one measures a child's language content ability is to look at their vocabulary and how well he understands, uses and describes vocabulary words.
