Contextual semantic functions of the nuclear sentence patterns in expending the communicative intention of the speaker and ways of their teaching

If it's raining now, then your laundry is getting wet.
If it's raining now, there will be mushrooms to pick next week.
If it rains this afternoon, then yesterday's weather forecast was wrong.
If it rains this afternoon, your garden party is doomed.
If it rains this afternoon, everybody will stay home.
If I become President, I'll lower taxes.
Certain modal auxiliary verbs (mainly will, may, might, and could) are not usually used in the condition clause (protasis) in English:
*If it will rain this afternoon, … *If it may have rained yesterday, …
There are exceptions, however, in which will is used exactly as in the first example, namely when the action in the if clause takes place after that in the main clause:
(The weather forecast says it's going to rain.) Well, if it will rain, we must take umbrellas.
If aspirins will cure it, I'll [I will] take a couple tonight instead of this horrible medicine.
Other situations in which will can be used in an if clause include when will is not being used as an auxiliary verb, in other words when it is being used modally to express willingness, persistence, or a wish:
If you'll [you will] just hold the door open for me a moment, I can take this table out to the kitchen.
If you will keep all the windows shut, of course you'll get headaches.
If you will excuse me, I think I will slip into something more comfortable.
In colloquial English, the imperative is sometimes used to form a conditional sentence: e.g. "go eastwards a mile and you'll see it" means "if you go eastwards a mile, you will see it". In counterfactual constructions, the condition clause expresses a condition that is known to be false, or presented as unlikely. The result clause contains a conditional verb form consisting of would (or could, should, might) plus a main verb in the base form (infinitive without to). The contrary-to-fact present conditional, often referred to as the "second conditional" or "conditional 2", is used to refer to a current state or event that is known to be false or improbable. The past subjunctive (or in colloquial English, simply the past tense) must be used:
If she were [colloq. was] at work today, she would know how to deal with this client.
If I were [colloq. was] the king, I could have you thrown in the dungeon.
The same structure can be used to refer to a future state or event:
If I won the lottery, I would buy a car. If he said that to me, I would run away.
In many cases, when referring to future events, the difference between a realis and irrealis conditional is very slight:
(realis) If you leave now, you can still catch your train.
(irrealis) If you left now, you could still catch your train.
The contrary-to-fact past conditional (sometime referred to as the "third" conditional, conditional 3) is used to refer to contrary-to-fact past events. The pluperfect (or past perfect) is used in the condition clause.
If you had called me, I would have come.
If you had done your job properly, we wouldn't be in this mess now.
Some varieties of English regularly use would (often shortened to (I)'d) and would have (often shortened to (I)'d have) in counterfactual condition clauses, but this is often considered non-standard: If you'd leave now, you'd be on time. (conditional 2.) / If you (would)'ve told me, we could've done something about it. (conditional 3.) Such use of would is widespread especially in spoken US English in all sectors of society, but these forms are not usually used in more formal writing. Nevertheless, some reliable sources simply label this usage as acceptable US English and no longer label it as colloquial. There are exceptions, however, where would is used in British English too in seemingly counterfactual conditions, but these can usually be interpreted as a modal use of would: If you would listen to me once in a while, you might learn something. (conditional 2.) In cases in which the action in the if clause takes place after that in the main clause, use of would in counterfactual conditions is however considered standard and correct usage in even formal UK and US usage: If it would make Bill happy, I'd [I would] give him the money. Should can appear in the condition clause to refer to a future event presented as possible, but unlikely, undesirable, or otherwise "remote":
If I should die before I wake, …
If you should ever find yourself in such a situation…
The sentence is the immediate integral unit of speech built up of words according to a definite syntactic pattern and distinguished by a contextually relevant communicative purpose. This definition proves that B.A. Ilyish is quite right when he writes: “The notion of sentence has not so far received a satis­factory definition.”² A sentence is a unit of speech whose grammatical structure conforms to the laws of the language and which serves as the chief means of conveying a thought. A sentence is not only a means of communicating something about reality but also a means of showing the speaker's attitude to it: The train moved out of the city. Are you ready? Put down the book. Thus, any act of communication there are three factors: the act of speech; the speaker; reality (as viewed by the speaker).
B. Khaimovich and Rogovskaya state that these factors are variable since they change with every act of speech. They may be viewed from two view­points: from the point of view of language are constant because they are found in all acts of communication; they are variable because they change in every act of speech. Every act of communication contains the notions of time, person and reality. The events mentioned in the communications are correlated in time and time correlation is expressed by certain grammatical and lexical means: Yesterday Anvar bought a car. They will do it tomorrow. Any act of communication presupposes existence of the speaker and the hearer. The meaning of person is expressed by the category of person of verbs. They may be expressed grammatically and lexico-grammatically by words: I, you, he...
I asked them to bring the chair into the dining room.
“He doesn’t know that” – said Andrew.
Reality is treated differently by the speaker and this attitude of the speaker is expressed by the category of mood in verbs. They may be expressed gram­matically and lexically (may, must, probably...)³: He must have forgotten to do it in time. Shahlo may come today. According to the same authors the three relations - to the act of speech, to the speaker and to reality - can be summarized as the relation to the situation of speech. The relation of the thought of a sentence to the situation of speech is called predicativity. Predicativity is the structural meaning of the sentence while intonation is the structural form of it. Thus, a sentence is a communication unit made up of words /and word-morphemes/ in conformity with their combinability and structurally united by intonation and predicativity. Within a sentence the word or combination of words that contains the meanings of predicativity may be called the predication.
My father used to make nets and sell them.
My mother kept a little day-school for the girls.
A proposition is the semantic invariant of all the members of modal and communicative paradigms of sentences and their transforms. But besides sentences which contain propositions there are interrogative and negative sentences. Speech is emotional. There is no one to one relationship. Then a sentence can be grammatically correct, but from the point of view of logic it won’t be correct, true to life. Laws of thinking are universal but there are many languages. Grammar and Logic don’t coincide: Water is a gas.