Conjunctions join words into phrases, clauses, and sentences. The coordinating conjunctions (FANBOYS) join two independent clauses: For, And, Nor, But, Or, Yet, So. They are always preceded by a comma.
Marta went to the pool, and Alex decided to go shopping.
Annie didn’t want to eat tacos for dinner, so she picked up a pizza on her way home.
We chose that restaurant because Juan loves pizza.
Correlative conjunctions (whether/or, either/or, neither/nor, both/and, not only/but also) work together to join items:
Both the teacher and the students needed a break after the lecture.
When using correlative conjunctions, be sure that the structure of the word, phrase, or clause that follows the first part of the conjunction mirrors the structure of the word, phrase, or clause that follows the second part.
Correct: I will neither mow the grass nor pull the weeds today.
Incorrect: I will neither be mowing the grass nor pull the weeds today.
Prepositions set up relationships in time (after the party) or space (under the cushions) within a sentence. A preposition will always function as part of a prepositional phrase, which includes the preposition along with the object of the preposition.
If a word that usually acts as a preposition is standing alone in a sentence, the word is likely functioning as an adverb (e.g., “She hid underneath.”)
Interjections have no grammatical attachment to the sentence itself other than to add expressions of emotion. These parts of speech may be punctuated with commas or exclamation points and may fall anywhere within the sentence.
Ouch! He stepped on my toe.