 The term adjunct is used to refer to an optional element in a construction. There are two interpretations of the term, a more traditional one, and one that relates to X-bar syntax. According to a more general approach, adjuncts are elements of clause structure that may be removed without the structural identity of the rest of the construction being affected. The clearest example at the sentence level is the adverbial. Here is an example. John saw the woman in the park, where John saw the woman, that is, the sentence without the adverbial, is grammatical, but John saw in the park is not. So in these examples, the adverbial, realized by a prepositional phrase, is an adjunct to C, whereas the noun phrase, the woman, is a complement. Note that there is no theoretical limit to the number of adjuncts. In other words, adjuncts can be stacked. Brutus stabbed Caesar, with a knife, in Rome, in 44 before Christ, in the eyes of March, and so on. In these examples, the prepositional phrases are adjuncts to stab, whereas the noun phrase Caesar is a complement. In X-bar syntax, the phrase structure representation format in generative grammar, adjuncts are defined structurally as sisters of X-bar and as daughters of another X-bar. So in Brutus stabbed Caesar with a knife, the prepositional phrase with a knife is an adjunct, it is a sister to verb bar, and a daughter to another verb bar. Since adding an adjunct may recursively expand X-bar into another X-bar, the number of adjuncts is theoretically unlimited.