Syntax. Part V. Conjunctions. Lesson 2. Subordinating conjunctions. Синтаксис. Часть V. Союзы. Урок 2. Подчинительные союзы.

The conjunctions given in the following examples are standard forms. They may all be used in all registers. It should be noted though that
subordinating conjunctions tend to occur more in higher register (i.e. in formal language, where a speaker or writer is perhaps concerned to establish the logical connections which conjunctions indicate) than in colloquial register, where language is more expressive and spontaneous and ideas less clearly organised, and where coordinating conjunctions therefore prevail.

Syntax. Part V. Conjunctions. Lesson 1. Coordinating conjunctions. Синтаксис. Часть V. Союзы. Урок 1. Сочинительные союзы.

(a) The main coordinating conjunctions (и, a, но, или) may be used in all registers. In colloquial speech, in which language tends to be spontaneous and less well organised, coordinating conjunctions are the principal means of linking the clauses of complex sentences and subordinating conjunctions play a lesser role. The following points about the Russian coordinating conjunctions should be particularly noted by the English-speaking student.