An abstract entity based on prototypical patterns found in utterances. In other words, a sentence is an idealisation that has determinate properties, often stated in terms of grammatical structure. For example, one definition of (an English) sentence might consist of the formula: S →NP VP. In this formula, 'S' stands for sentence, 'NP' for subject noun phrase and 'VP' for the verb phrase or predicate which provides information about the subject NP. The notion of a sentence, while based on prototypical patterns found in utterances, is not the same as an utterance. Much of formal linguistics has been concerned with modelling the properties of language that enable us to produce grammatically well-formed sentences. Typically, cognitive linguistics places little emphasis on the sentence as a theoretical entity. In contrast, the notion of a usage event or utterance is central to the cognitive perspective.