adjectives in a sentence, which become predicate nouns and predicate adjectives. Copulae are thought to 'link' the predicate adjective or noun to the subject. They can also be followed by an adverb of place, which is sometimes referred to as a predicate adverb. For example: "My house is down the street." The main copular verb be is manifested in eight forms be, is, am, are, was, were, been, and being in English. Valency The number of arguments that a verb takes is called its valency or valence. Verbs can be classified according to their valency: Avalent (valency = 0): the verb has neither a subject nor an object. Zero valency does not occur in English; in some languages such as Mandarin Chinese, weather verbs like snow(s) take no subject or object. Intransitive (valency = 1, monovalent): the verb only has a subject. For example: "he runs", "it falls". Transitive (valency = 2, divalent): the verb has a subject and a direct object. For example: "she eats fish", "we hunt nothing". Ditransitive (valency = 3, trivalent): the verb has a subject, a direct object, and an indirect object. For example: "He gives her a flower" or "She gave John the watch." A few English verbs, particularly those concerned with financial transactions, take four arguments, as in "Pat1 sold Chris2 a lawnmower3 for $204" or "Chris1 paid Pat2 $203 for a lawnmower4". Impersonal and objective verbs Weather verbs often appear to be impersonal (subjectless, or avalent) in null-subject languages like Spanish, where the verb llueve means "It rains". In English, French and German, they require a dummy pronoun and therefore formally have a valency of 1. However, as verbs in Spanish incorporate the subject as a TAM suffix, Spanish is not actually a null-subject language, unlike Mandarin (see above). Such verbs in Spanish also have a valency of 1. Intransitive and transitive verbs are the most common, but the impersonal and objective verbs are somewhat different from the norm. In the objective, the verb takes an object but no subject; the nonreferent subject in some uses may be marked in the verb by an incorporated dummy pronoun similar to that used with the English weather verbs. Impersonal verbs in null subject languages take neither subject nor object, as is true of other verbs, but again the verb may show incorporated dummy pronouns despite the lack of subject and object phrases. Valency marking