1. Subject of theoretical grammar. Analytic and synthetic word forms

one-member sentence”, “one-axis sentence”, or “elliptical sentence”.
As for negation and affirmation formulas (Yes; No; All right), vocative sentences (Ladies and gentlemen! Dear friends!), greeting and parting formulas (Hello! Good-bye!) and other similar constructions, they constitute the periphery of the category of the sentence: they are not exactly word-sentences, but rather sentence-representatives, related to the corresponding two-axis sentences not by “vague” implications, but by representation. Most of them exist only in syntagmatic combinations with full-sense antecedent predicative constructions. Cf.: Are you going to come? – No (= I am not going to come). The isolated exclamations of interjectional type, like My God! For heaven’s sake! Gosh!, etc., are not related to any two-axis constructions at all, either by vague implications or by representation, being “pseudo-sentences”, or “non-communicative utterances” and rendering no situational nomination, predication or informative perspective of any kind (see Unit 22).
The semantic classification of simple sentences is based on principal parts semantics. On the basis of subject categorial meaning, sentences are divided into impersonal, e.g.: It drizzles; There is no use crying over spilt milk; and personal; personal sentences are further subdivided into human and non-human. Human sentences are further subdivided into definite, e.g.: I know it; and indefinite, e.g.: One never knows such things for sure. Non-human sentences are further subdivided into animate, e.g.: A cat entered the room; and inanimate, e.g.: The wind opened the door. Impersonal sentences may be further subdivided into factual, e.g.: It drizzles; and perceptional, e.g. It looks like rain.
On the basis of predicate categorial meaning, sentences are divided into process featuring (“verbal”) and substance featuring (“nominal”); process featuring sentences are further subdivided into actional, e.g.: I play ball; and statal, e.g.: I enjoy your party; substance featuring sentences are further subdivided into factual, e.g.: She is clever; and perceptional, e.g.: She seems to be clever. As the examples show, the differences in subject categorial meaning are sustained by obvious differences in the subject-predicate combinability.
In practical courses on grammar, various subdivisions of simple sentences are usually based on the structure of the predicate: predicates are subdivided into simple (I read) and compound, which are further subdivided into compound verbal predicates (She started crying) and compound nominal predicates with pure and specifying link verbs (She looked beautiful).
On the basis of subject-object relations, simple sentences are divided into subjective, e.g.: He is a writer; objective, e.g.: He is writing a book; and neutral or “potentially” objective, e.g.: He is writing.