An interjection is a word or phrase that expresses emotion and is separated from the rest of the sentence by a comma or exclamation point. Interjections are not grammatically necessary parts of sentences. Examples include "Oh, I wish I could help you" and "Wow! You did a great job!" A conjunction connects words, phrases, or clauses within a sentence. There are coordinate conjunctions like "and", "or", and "but" and correlative conjunctions which always come in pairs like "both/and" and "either/or". Conjunctions join elements of the same type, like nouns to nouns.