A noun is a word that stands for a person, like the word "farmer," a place, such as "highway," or a thing, such as a "truck." In the sentence "The farmer drives his truck on the highway," the words farmer, truck and highway are nouns. An adjective is word that describes a noun, such as tall, beautiful or friendly. In the sentence "The tall farmer drives his old truck," the words tall and old are adjectives. They are used to further describe the words farmer and truck.
Verbs are action words such as drive, walk, swim or jump. They describe the action a noun is performing in a sentence. For example, "The farmer swims" or "The farmer walks." An adverb is a word that describes how the action is performed, such as slowly or happily. Examples are "The farmer swims happily" or "The farmer walks slowly."
A pronoun is a word that stands in for a noun. These can be personal pronouns such as I, you or he; possessive pronouns like mine, yours and hers or interrogative pronouns like who or what. Some pronouns are indefinite like anybody, everybody, or another; these words may function as adjectives depending on the sentence. For example, in the sentence "One might say that," the word "one" is a pronoun. In the sentence "One drink is enough," the word "one" is an adjective describing the word "drink."
There are also relative pronouns like whose, which or that. These pronouns refer to a noun and introduce a clause relating to it, such as in the sentence, "The bike, which I bought in May, is already broken." In all cases a pronoun is a word which refers to a noun or noun phrase which has already been introduced or can be inferred.
A preposition is a word that usually comes before a noun or pronoun and describes that word's relationship to another word. The words "after" and "to" are both prepositions. For example, in the sentence "She arrived after dinner," the word "after" describes the noun's relationship to the verb. When did she arrive? After dinner. These are often directional words like under, over, above, in or behind. In the sentence "She went to school," the word "to" is a preposition.
A conjunction is a word that connects two sentences, clauses, phrases or words. These are words like but, which introduces a contrasting idea; and, which introduces something not contrasting; and so, which introduces a consequence. For example, "He runs three times a week, but still hasn't quit smoking", "He swims two days a week, and runs three times," "He swam all day, so he has gone to bed early." These are coordinating conjunctions, which connect two terms. There are also subordinating conjunctions that connect a subordinate clause to a main clause, such as although or because. For example, "I ran today, although my ankle hurt."
An interjection is a short exclamation used more often in speech than writing, but in either case an isolated expression without a grammatical relation to the rest of the sentence. Words like "hello" or "goodbye," or expressions such as "excuse me" and "cheers," are interjections. These words will often be seen as a standalone sentence, as in "Hello! How are you?" or will be separated from other clauses by a comma. Profanity often appears as interjections, as does its substitute expressions.