The word "arbitrary" is an adjective. It is used to describe something that is based on random choice or personal whim rather than any reason or system. For example, one might say, "The rules seemed arbitrary and lacked a clear rationale."
The word impetuous is an adjective. It describes someone who makes arbitrary decisions.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "explicit" is an adjective.
The part of speech for "twirl" is a verb.
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "lecturer" is a noun.
The part of speech for "indefinite" is an adjective.