The study of the constituent structure of the sentence presupposes the analysis of its parts. Scholars traditionally distinguish between the main and the secondary parts.
The simple sentence, as any sentence in general, is organised as a system of function-expressing positions, the content of the functions being the reflection of a situational event. The nominative parts of the simple sentence, each occupying a notional position in it, are subject, predicate, object, adverbial, attribute, parenthetical enclosure, addressing enclosure; a special, semi-notional position is occupied by an interjectional enclosure. The parts are arranged in a hierarchy, wherein all of them perform some modifying role.
Thus, the subject is a person-modifier of the predicate. The predicate is a process-modifier of the subject-person. The object is a substance-modifier of a processual part (actional or statal). The adverbial is a quality-modifier (in a broad sense) of a processual part or the whole of the sentence (as expressing an integral process inherent in the reflected event). The attribute is a quality-modifier of a substantive part. The parenthetical enclosure is a detached speaker-bound modifier of any sentence-part or the whole of the sentence. The addressing enclosure (address) is a substantive modifier of the destination of the sentence and hence, from its angle, a modifier of the sentence as a whole. The interjectional enclosure is a speaker-bound emotional modifier of the sentence.
Syntactic processes include: expansion, compression, addition, specification, complication, contamination, inclusion, isolation, substitution, ellipsis.