The sentence is a unit of speech built up of words according to a definite syntactic pattern and distinguished by a contextually relevant communicative purpose.
The most essential features of the sentence are:
1) it is a predicative unit (it (1) presents the referents as making up a certain situation/event, and (2) reflects the connection between the nominal denotation of the event on the one hand, and objective reality on the other).
2) it is intonationally delimited.
3) it is characterised by a definite standard syntactic-semantic features.
4) it possesses syntactic modality.
5) it has a nominative function (substance namimg).
The sentence can be analyzed on the basis of various approaches:
1) Principal and secondary parts of the sentence.
2) Immediate constituents of the sentence (IC analysis). It aims at the principles of word arrangement in the sentence. Each language has its own way of structural grouping. English has dichotomous phrase structure, which means that the phrase in English can always be divided into two elements (constituents) until we get down to the single word. All groups of words are arranged in levels. The name given by linguists to these different levels of relationship is immediate constituents. Thus, one way of analyzing a sentence is to cut it to its immediate constituents, that is, to single out different levels of meaning (old men and women)
3) Oppositional analysis.
The oppositional method in syntax means correlating different sentence types: they possess common features and differential features. Differential features serve the basis for analysis (two member sentence – one member sentence (John worked – John! Work!)
4) Constructional analysis.
According to the constructional approach, not only the subject and the predicate but also all the necessary constituents of primary predication constitute the main parts because they are constructionally significant. Therefore, the secondary parts of the sentence are sometimes as necessary and important as the main ones.