Every word in a sentence can be identified as one of the eight parts of speech. Nouns define a person, place, thing or idea. Pronouns are used in the place of a noun. Verbs show an action or a state of being (is, am, was). Every sentence needs a verb. Contemporary use of speech dilutes the power of a verb and can make a noun look like an action. In the statement, "Jane gave Jim a shove," shove is a noun. Shove becomes a verb when that same sentence is written, "Jane shoved Jim."
Adjectives and adverbs are two parts of speech often confused. Adjectives describe a noun or pronoun. Adverbs modify verbs, other adverbs and adjectives. If you should receive a very long email, the word very is considered an adverb because it modifies long, an adjective. Adjectives and adverbs usually appear before the words they modify. They can appear in other parts of the sentence, separated from the word they describe. Consider the sentence: "The fog was dense." In this case, dense is an adjective separated from the noun it modifies by a verb. This can be further confused by more a more complex sentence: "The white fog was dense." Both white and dense are adjectives describing fog.
Prepositions and conjunctions are both parts of speech that connect words. These can be the parts of speech most difficult to identify. Prepositions connect nouns and pronouns to the rest of the sentence. They often tell where the noun is in time or space: under, before, in, out. Other common prepositions are by, with, about and from. Conjunctions connect phrases or clauses as well as words. And, but, or, while, for, so and because are common conjunctions. These connecting words can be confused. A good rule of thumb is to put the questionable word before a noun, like "the box." If it makes sense, it is probably a preposition.
Interjection is the eighth part of speech. These are words that show emotion, often appearing alone in a sentence. "Wow!" is an example of an interjection.
There is some debate that the list is not a complete with eight parts of speech. Grammarians question the role of "the" or "to" when it appears before a verb. Neither of these words fits neatly into one of the traditional eight parts of speech. "The" was assigned as an adjective and "to" as a preposition. Some disagree with this decision, and some textbooks may reflect this disagreement with additional parts of speech that re-categorize these two words.