Is about a preposition?
About is a preposition or an adverb.
Prepositions and postpositions, together called adpositions, are a class of words used to express spatial or temporal relations or mark various semantic roles. A preposition or postposition typically combines with a noun phrase, this being called its complement, or sometimes object.
A preposition is a word or group of words used before a noun, pronoun, or noun phrase to show direction, time, place, location, spatial relationships, or to introduce an object. Some examples of prepositions are words like "in," "at," "on," "of," and "to." Prepositions in English are highly idiomatic.
