Composing unions are an auxiliary part of speech. They serve as a connecting link connecting both parts of a complex sentence and its homogeneous members. It should be remembered that the unions themselves cannot be members of the proposal.
By type of communication in the proposal, unions are divided into four groups.
1. Connecting unions that are used in a complex sentence or with homogeneous sentence members: and, yes (in the meaning of "and"), and, no, no, also. Single connecting unions with homogeneous members do not require a comma. In all other cases (in a compound sentence or when repeating a union), a comma is simply necessary within the group of homogeneous members of the sentence. When repeating one and the same union in a group of homogeneous members, the comma begins to be placed before the second use of the union.
2. Opposing unions - a, but, yes (= but), but, however. They contrast one option with another, for example: I went for a walk, but the rain drove me away.
3. Separation unions - or, or, somehow, not that - not that, or - or that. These unions also provide options. For example: Will we cook mashed potatoes with a patty or pasta with goulash today? On the street it’s either rain or snow.
4. Comparative unions are mainly double or compound. This: both ... and; not only but; not so much ... how much; not like; although ... but; not that (would) ... but (a); if not ... then. Examples: I really like to walk both in fine weather and in the rain. Although it was raining, the sun continued to shine.
With a more detailed study and research, you can find as many as 7 groups of unions, that is, three more will be added to the well-known four: gradational, connecting, explanatory. In addition to the fact that compositional unions are divided by value, they are also classified by structure into simple one-word (and how, but) derivatives (also), compound (since), non-derivatives (and, but, or) , single (however), repeated (and ... and neither ... nor), double (both ... and).
It is necessary to dwell in more detail on the spelling of derivative unions “but” and “also”. They are often confused with the indicative pronoun "that" with the pretext "for" or with the particle "same" and vice versa. As a result, a union can be written in two words, and a pronoun with a preposition or a particle is merged into one, which, of course, is a gross, but extremely widespread mistake. In order not to make a mistake in writing, you should just try to ask a question “for something” or “on the other hand”, and if you succeed, it means we have a pronoun, and we should write it in two words. For example: I fell in love with the Russian language already because the great Pushkin wrote on it. We ask a question: fell in love (for what?) For that.
The opposite example: there was not enough money for sausage, but Tanyusha bought ice cream. In this option, the question cannot be asked, but the union “but” is easily replaced by another union, for example, “and”. This option will turn out: There was not enough money for the sausage, and Tanyusha bought ice cream. Simple compositional unions are one-word, and compound unions consist of two or more words. Derivative unions are representatives of several parts of speech, mainly union and adverb. Non-derivative unions have always been only unions and have no connection with other parts of speech. Unions consisting of one word, as well as indicating the exhaustive nature of the definition, are called "single composing unions." Examples: I thought I would go to the movies, but we went to the theater. It rained for a whole week, and mushrooms climbed out from the ground with whole mushroom lawns.
Linguists, exploring sentences with creative conjunctions that are repeated in a sentence, believe that they enhance the contrast of the listing, for example: They were wrong: neither I went nor she went. Between the parts of the double union is always a homogeneous member of the sentence, after which you need to put a comma. But also a simple sentence, which is part of a complex one, can take its place.
Separately, it is worth clarifying that it is necessary to remember and be able to distinguish the union itself from the union word. “How to distinguish them and what are allied words?” - the reader will ask. Make it easier than it might seem at first glance. Allied words - words that play the role of unions, but not related to this part of speech. To determine what is before us, simply ask a question. Since it is easy to ask a question to union words , but it is impossible for the union, this fact is decisive here. This also implies that the union words can be defined as a member of the sentence, which cannot be done with respect to the union.