Correlative Conjunctions Correlative conjunctions always appear in pairs -- you use them to link equivalent sentence elements. The most common correlative conjunctions are "both...and," "either...or," "neither...nor,", "not only...but also," "so...as," and "whether...or." (Technically correlative conjunctions consist simply of a co-ordinating conjunction linked to an adjective or adverb.) The highlighted words in the following sentences are correlative conjunctions: Both my grandfather and my father worked in the steel plant. In this sentence, the correlative conjunction "both...and" is used to link the two noun phrases that act as the compound subject of the sentence: "my grandfather" and "my father". Bring either a Jello salad or a potato scallop. Here the correlative conjunction "either...or" links two noun phrases: "a Jello salad" and "a potato scallop." Corinne is trying to decide whether to go to medical school or to go to law school. Similarly, the correlative conjunction "whether ... or" links the two infinitive phrases "to go to medical school" and "to go to law school." The explosion destroyed not only the school but also the neighbouring pub. In this example the correlative conjunction "not only ... but also" links the two noun phrases ("the school" and "neighbouring pub") which act as direct objects. Note: some words which appear as conjunctions can also appear as prepositions or as adverbs.

Subordinating Conjunctions A subordinating conjunction introduces a dependent clause and indicates the nature of the relationship among the independent clause(s) and the dependent clause(s). The most common subordinating conjunctions are "after," "although," "as," "because," "before," "how," "if," "once," "since," "than," "that," "though," "till," "until," "when," "where," "whether," and "while." Each of the highlighted words in the following sentences is a subordinating conjunction: After she had learned to drive, Alice felt more independent. The subordinating conjunction "after" introduces the dependent clause "After she had learned to drive." If the paperwork arrives on time, your cheque will be mailed on Tuesday. Similarly, the subordinating conjunction "if" introduces the dependent clause "If the paperwork arrives on time." Gerald had to begin his thesis over again when his computer crashed. The subordinating conjunction "when" introduces the dependent clause "when his computer crashed." Midwifery advocates argue that home births are safer because the mother and baby are exposed to fewer people and fewer germs. In this sentence, the dependent clause "because the mother and baby are exposed to fewer people and fewer germs" is introduced by the subordinating conjunction "because."

You can use a conjunction to link words, phrases, and clauses, as in the following example: I ate the pizza and the pasta. Call the movers when you are ready. Co-ordinating Conjunctions You use a co-ordinating conjunction ("and," "but," "or," "nor," "for," "so," or "yet") to join individual words, phrases, and independent clauses. Note that you can also use the conjunctions "but" and "for" as prepositions. In the following sentences, each of the highlighted words is a co-ordinating conjunction: Lilacs and violets are usually purple. In this example, the co-ordinating conjunction "and" links two nouns. This movie is particularly interesting to feminist film theorists, for the screenplay was written by Mae West. In this example, the co-ordinating conjunction "for" is used to link two independent clauses. Daniel's uncle claimed that he spent most of his youth dancing on rooftops and swallowing goldfish. Here the co-ordinating conjunction "and" links two participle phrases ("dancing on rooftops" and "swallowing goldfish") which act as adverbs describing the verb "spends."

the word which can join two sentences , cf. and however while ,but ,

A conjunction is a joining word! eg and, but, although etc.