The main members of the proposal are subject and predicate, secondary - definition, circumstance and addition. However, this separation, which has become traditional, involves a rather high level of abstraction, since in order to identify the difference it is necessary to distract from the multitude of linguistic facts. We will try to highlight the main members of the proposal.
We cut off the communicative structure
First of all, one should cut off the communicative structure of one or another sentence related to a specific speech situation. On this side, the difference between the secondary and main members is not significant, since any of them, and not just the main one, may turn out to be more important in this aspect. So, when answering the question "When did Pyotr Petrovich arrive?" in the sentence “Petr Petrovich arrived the day before yesterday,” “the day before yesterday,” which is secondary, will be more significant. From a communicative point of view, the main members of a sentence are not always such. Sometimes they are secondary.
We discard the semantic factors
To determine the main members of the proposal, it is necessary to drop all the factors that are associated with its meaning. The definition of subject and predicate within traditional boundaries does not take into account the fact that not with each of their lexical expressions or the main term in some monolithic, an unexplained sentence can be obtained . So, for example, it is difficult to use in speech such ones as “He found himself”, “He lost”, “The apartment consists”, etc.
The analysis, thanks to which the main language of the sentence and the other minor ones, is distinguished by the Russian language, does not take into account all such facts. This is because it is not aimed at a speech lexical unit, but at its abstract scheme. Therefore, for these purposes, the fact that often secondary ones are mandatory is also unimportant, since they specify or supplement the indefinite or inferior main members of the proposal.
They make up the division of the sentence members, distracting, for example, from the fact that the semantic structure of the secondary may be as necessary as the subject and predicate. This must be borne in mind when analyzing.
The concept of the main members
The main members of the sentence are subject and predicate. Allocation of them traditionally lies in the formal sphere. Only here is the difference between the nominative case of the subject and other indirect cases characteristic of additions with the value of the subject. It consists in the fact that this form (that is, the subject) is in interaction with the predicate, and not one-sidedly dependent on it, which is observed in all forms of other, indirect cases (including subjective meaning).
Subject
The subject not only depends on it, but also determines the form of the predicate in relation to the categories of gender, number and person. Such an invariable rule offers us the Russian language.
The main members of the sentence include a noun in the nominative case (subject), which is in conjunction with the predicate. This is because it participates in the formation of the predicative center of the whole sentence.
Predicate
The predicate as a member has two characteristics: it is a carrier, an exponent of predicativity and is consistent with the subject. Observations of how it expresses predicative categories in different sentences contributed to the creation of a detailed theory of predicate types, thanks to which ideas for creating a list of various structural schemes of sentences in relation to the two-component were largely realized.
Predicate types
Distinguish between simple and compound, as well as verbal and nominal predicate. A verb can be either simple or compound, and a nominal one is always compound. All of these types are the main members of the proposal. The subject does not have such a separation.
Only one component consists of a simple predicate. This can be a conjugated form of the verb or its substitute, infinitive or verb interjection.
One-part sentence, allocation of its main member
The idea that the predicate is a member of the sentence, which depends on the subject and therefore necessarily assumes its presence, served as the basis for highlighting another main member of the sentence, the third in a row, which is called the main member of the one-part sentence.
It has long been noted that there are those where only one principal member is possible. However, only A.A. Chess into one type, called "one-part" sentences, combined all such cases and contrasted them with "two-part" sentences, in which the subject and predicate are necessarily present.
In a one-part sentence, the main term is a special phenomenon of syntax, since it alone makes up the predicative basis of the whole sentence. That is, like a predicate, it is a carrier of such a property as predicativity. The similarity with him is also manifested in the fact that this member has the same types as the predicate. However, unlike the latter, the form of which by some of its parties (gender, number, person) depends on the subject, in a one-part sentence the main member does not adapt in form to any of them, since it is absolutely definable, peculiar only to a one-part sentence.