Prepositions, Coordinating Conjunctions, and Subordinating Conjunctions

Prepositions are words that connect a noun or pronoun with another part of a sentence. Prepositions almost always introduce a noun or pronoun, which is called the object of the preposition.

Conjunctions are used to connect words and groups of words in a sentence. There are two major types of conjunctions: coordinating conjunctions and subordinating conjunctions.

Coordinating conjunctions join equivalent words or word groups. They are used with commas for items in series and to avoid run-ons when joining independent clauses. One easy way to remember the coordinating conjunctions is to use the mnemonic "FANBOYS":

1. For
2. And
3. Nor
4. But
5. Or
6. Yet
7. So

Meanwhile, subordinating conjunctions make one independent clause subordinate to, or dependent on, another. Whether a comma is needed with a subordinating conjunction depends on the placement and function of the subordinating conjunction. A comma is needed when the subordinating conjunction and its clause is first in the sentence. If the subordinating conjunction is between the clauses, a comma is sometimes needed to show contrast.

There are many subordinating conjunctions. Common ones include after, although, as, because, before, once, since, unless, until, when, and while.