5-1. Coordinators

Процитируем 'Longman student grammar of spoken and written English':

Here are two types of words traditionally called conjunctions in English: coordinators (also called coordinating conjunctions), and subordinators (or subordinating conjunctions). Coordinators are used to indicate a relationship between two units such as phrases or clauses. Coordinators link elements which have the same syntactic role, and are at the same level of the syntactic hierarchy.

Thus, in any structure [X + coordinator + Y], X and Y are equivalent. The main coordinators are and, but, and or. In the following examples, the coordinated elements are marked by [ ]:

[Mother] and [I] saw it.
[I don't want to speak too soon], but [I think I have been fairly consistent this season].
Is this necessarily [good] or [bad]?

Or has a rather infrequently used negative counterpart, nor, which is used after negative clauses:

[The donkeys did not come back], nor [did the eleven men], nor [did the helicopter].

As this example shows, coordinators can be used to connect more than two elements.