On March 31st I found that Helen knew eighteen nouns and three verbs.
She makes many mistakes, of course, twists words and phrases, puts the cart before the horse, and gets herself into hopeless tangles of nouns and verbs; but so does the hearing child.
Each of the personal pronouns (except the 3rd plur.) exists in a longer and a shorter form: the one is used as a nominative and is a separate word, the other is attached to verbs and (in a slightly different form) to nouns to express the accusative or genitive.
Many words are used indiscriminately as nouns, adjectives or verbs, without any change of form.