Gerunds and Infinitives are words or phrases that appear to be verbs—action words— but actually function as nouns. Gerunds are formed by adding “–ing” to a verb: reading, swimming, playing. Infinitives are formed by adding “to” before a verb: to read, to swim, to play. They can function as either the subject of a sentence: Reading is my favorite hobby; or as the object of a verb: He likes to read.