Conjunctions

Conjunctions join words, phrases, or clauses and are classified as coordinating conjunctions or subordinating conjunctions.

Coordinating Conjunctions
The most common coordinating Conjunctions are and, but, for, nor, or, so, and yet. Note that so and yet may also act as subordinating conjunctions.

Consider the following sentences, each of which has a coordinating conjunction:

She and I are bridge partners.(Coordinating conjunction joining pronouns.)
He or I will stay behind.(Coordinating conjunction joining pronouns.)
The bed in our room or the one in the guest room should be replaced.(Coordinating conjunction joining phrases)
He quickly decided to run for mayor, but just as quickly withdrew.(Coordinating conjunction joining clauses.)
There is enough time to finish the book, for we still have an hour before dinner. (Coordinating conjunction joining clauses)

Other coordinating conjunctions are the so-called correlatives, which occur in pairs: either...or, neither...nor, not only...but also, and both....and. The correlatives are used to join sentence elements having equivalent value. Consider the following sentences:

Either you do the dishes now or I will do them later.
Neither my mother nor my father saw much of me from then on.
Not only has the Security Council imposed sanctions, but many countries are suggesting armed intervention.
Not only does she write poetry, but she also writes short stories.
Both sushi and broiled fish were served to the guests.

Subordinating Conjunction
Subordinating conjunctions connect clauses of less than equivalent value. The most common subordinating conjunctions are after, although, as, as if, as long as, because, before, how, if, in order that, since, so, so that, though, till, unless, until, when, where, wherever, while, why, and yet. The relative pronouns that, what, which, and who also act as subordinating conjunctions.Consider the following sentences.

I will take over the nursing duties after the nurse leaves.
You and I cannot tale all the credit for our success. although we did a great deal of the work.
The Kenners arrived at the party before most of the other guests showed up.
All students have been studying Spanish since they entered third grade.
The sad day will surely arrive when the mortgage interest will increase.
Mickey sat in the library while Sam was out on the tennis court.