In grammar, a conjunction is a part of speech that connects two words, phrases, or clauses together. This definition may overlap with that of other parts of speech, so what constitutes a "conjunction" should be defined for each language. In general, a conjunction is an invariable grammatical particle, and it may or may not stand between the items it conjoins.
The definition can also be extended to idiomatic phrases that behave as a unit with the same function as a single-word conjunction (as well as, provided that, etc.).
TYPES OF CONJUNCTIONS
Coordinating conjunctions, also called coordinators, are conjunctions that join two items of equal syntactic importance. As an example, the traditional view holds that the English coordinating conjunctions are for, and, nor, but, or, yet, and so (which form the mnemonic FANBOYS). Note that there are good reasons to argue that only and, but, and or are prototypical coordinators, while nor is very close. So and yet share more properties with conjunctive adverbs (e.g., however), and "for...lack(s) most of the properties distinguishing prototypical coordinators from prepositions with clausal complements" . Furthermore, there are other ways to coordinate independent clauses in English.
Correlative conjunctions are pairs of conjunctions which work together to coordinate two items. English examples include both … and, either … or, neither … nor, and not (only) … but (… also).
Subordinating conjunctions, also called subordinators, are conjunctions that introduce a dependent clause. English examples include after, although, if, unless, and because. Another way for remembering is the mnemonic "BISAWAWE": "because", "if", "so that", "after", "when", "although", "while", and "even though". Complementizers can be considered to be special subordinating conjunctions that introduce complement clauses (e.g., "I wonder whether he'll be late. I hope that he'll be on time").
In many verb-final languages, subordinate clauses must precede the main clause on which they depend. The equivalents to the subordinating conjunctions of non-verb-final languages like English are either
clause-final conjuctions (e.g. in Japanese) or;
suffixes attached to the verb and not separate words