The constituents of a sentence are the verb, its arguments and adjuncts. Arguments are the obligatory constituents of the sentence. Each of the arguments of the verb within a clause has a specific grammatical function. The grammatical functions are subject, direct object, and indirect object [Syntax - 2.1.]. Adjuncts are modifiers of the verb phrase, typically expressing a locational, temporal or a manner relation. Adjuncts are optional.