Today it is a challenge to get a proper solution in terms of linguistics. Significant contribution to the development of this problem has made A. A. Shakhmatov

CHAPTER 1 THE HISTORY OF FORMATION AND DEVELOPMENT OF THE PROBLEM OF TYPES OF SENTNECES

1. 
   The substantial essence of concepts "sentences", "composing" and "submission"
   

The problem of types of sentences is investigated by different scientists. They were reflected under the editorship of V.G. Arakina , A.A. Shakhmatov, N.M. Shanskiy , V.G. Admoni and many others. In the beginning, they reveal the essence of understanding the "sentences". The most interesting of them tells O. B. Sirotinina, emphasizing the sentence as a syntactic level together with the phrase.
So, by the word “sentence”, we mean the phrase that is a free combination of words which makes it possible to create an innumerable number of options necessary for constructing a sentence and thereby expressing thoughts. "The units of the syntactic level are not specific phrases and sentences, but models of their production"[42, 26]
The problem of the types of sentences in linguistics has its own history. One of the first functions on the difference was given little attention.
So, the main function of a sentence that distinguishes it from other linguistic units, for example, from a word or phrase, is "the formation, expression and communication of thought about some reality." This function of the sentence is called predicative. A predicative function can be a separate sentence, and a sentence as part of the text. In the first case, the predicative function of the sentence is supported by a communication situation that replaces the context. Here is a short excerpt from A. Livanov's book "L. D. Landau: 
At the Institute of Physical Problems, Landau found his original home (1). With him, life and fate were tied to the end (2).Was together in the days of peace, and in the days of war (3). In the summer of 1941 the institute was evacuated to Kazan (4). There, like the rest of the staff, Landau gave his strength , first of all, defense tasks (5). He built theories and calculated the processes that determine the combat capability of weapons (6). In 1945, when the war was over, three articles by Landau on detonation of explosives appeared in the "Reports of the Academy of Sciences" (7). In each, along with the Institute of Physical Problems, there is another "address" - the Engineers' Committee of the Red Army (8):
These sentences are considered N.M. Shanskiy, justifying the grammatical functions of sentences. He emphasizes that "each sentence in its predicative function is related to the preceding and subsequent. Thus, in Proposition 1 the predicative function is to inform the reader that the Institute of Physical Problems became for Landau, the Soviet theoretical physicist, the real house. The following two sentences repeat, refine and strengthen what was said in Proposition 1. Propositions 4-8 illustrate and unfold what was said in Proposition 3. However, along with this, each of them has its own predicative function: the fourth one reports the evacuation of the institute in Kazan, in the fifth - on the return of the staff of the Institute and Landau all the forces of defense tasks, etc. Sentences in the text have some features: the name of the scientist Landau is replaced by the pronoun he (6); instead of repeating the phrase three articles, the author uses the word every (8), etc. This happens because the sentence is included in the text, is influenced by other sentences and influences them. First of all , this refers to the predicative function of a sentence: the predicative function of each sentence is formed ( understood by the listener or the reader) in connection with other sentences or, if the sentence is single, in connection with the situation preceding the context, drawing, photography, etc."[48, 530]
The concept of A.I. Smirnitskiy and his type clearly gave a sentence in the book "The Syntax of the English Language."
"A sentence is the order of words that expresses a completed thought. In speech, they are determined by intonation, on the letter by punctuation. The true act of speech is a sentence or a chain of sentences. That is why the sentence stands out as a unit of speech, and at the same time as the basic unit of speech"[44, 50]
V.D. Arakin in one of his books asserts that in the sentence the character of the tone movement and the nature of the completion of the syntagma allowed to allocate the sentence in the collated languages ​​in preliminary order three types of syntagmas:
1) the type of syntagma with a decreasing scale, divided into three subtypes: a) a subtype with a descending completion - exists in Russian, English; b) subtype of syntagmas with a descending tone and an ascending end - is presented both in Russian and in English for registration of unfinished sentences preceding another 
sentences; c) subtype of syntagmas with decreasing scale and equal completion - prepares introductory sentences in Russian and English languages;
2) the type of syntagma with an increasing scale, represented by two subtypes: a) a subtype of syntagmas with an ascending end, widespread in Russian interrogative sentences, not typical for English; b) a subtype of syntagmas with a descending completion that forms Russian interrogative sentences, beginning with the word "unless", etc., is absent in English;
3) the types of syntagmas with an even scale, used in Russian for the formulation of interrogative sentences repeating the question, introductory words and sentences, and so on.
Pavel Alexandrovich Lecant gives a different characteristic to the sentence, calling it a communicative unit, that is, a function of the message, and also considers in detail each type of sentence on the purpose of the utterance.
In his textbook "Modern Russian Language" the sentence is interpreted as "the main means of expressing and communicating thoughts. Communicative function cannot be done with a word, with phraseology, or with a word combination: they are the names of objects, signs, actions"[30, 462]
The sentence calls the situation, the event. According to PA Lecant, predicativity and intonation are the specific features of a sentence that distinguish it from other units of language. Thus, he considers these two components together with the general concept of the sentence and does not share them.
Intonation is a complex phonetic phenomenon. It performs a variety of functions:
1) Complete the sentence; 
2) Expresses the emotional side of the speaker, affects the feelings of the hearer; 
3) In speech, pursuing the types of influence, expresses volitional impulses; 
4) Expresses the modal shades of the sentence.
The central grammatical unit of syntax is a simple sentence - a monopredicative syntactic unit, which is an elementary unit intended for the transmission of relatively complete information and possesses such properties that make it possible to classify the time plan as reported.
The grammatical meaning of a simple sentence is predicativity, a category that relates a message to a particular time plan of reality with a whole complex of formal syntactic means. That way, the block diagram of sentences has grammatical properties that allow you to indicate that what is being reported about, or is actually realized in time (present, past, future), that is, has a real time plan, or is conceived as possible, proper, desired, that is, has a surreal plan, or a temporary uncertainty.
The values ​​of time and reality / unreality are merged together, their complex is called objective modality.
Thus, the concept of predicativity as an abstract syntactic category consists of concepts: the structural scheme, the temporal plan of the reported and the reality / unreality of the reported. [50,409]
The main means of forming predicativity is the category of inclination, with the help of which the message appears in the aspect of reality / unreality.