It is now pertinent to make some observations about the distribution of the copulative verbalizer. This is the same element which developed into copulative "a" in Ancient Greek. Within copulative clauses, however, there are restrictions. Pronouns behave in many ways like nouns, having locative, possessive and copulative forms. Because many of these copulative verbs may be used non-copulatively, examples are provided. A verb that is a copula is sometimes called a copulative or copular verb. Copulative, adversative and disjunctive notions are typically communicated by context or clause order. Copulative compounds are compounds with two semantic heads. Instead of the more traditional copulative term 'is', Bolzano prefers 'has'. The substantive possessive forms of a noun also have a copulative of their own. Crowell (1979) divides these clauses, which he calls "copulative", into "existential", "equative" and "identificational". The copulative form always uses the identifying prefix "yi-". However Acanthozoon possess only a single male copulative organ contrary to Thysanozoon.