How to know if the word is adverb

Well, an adverb is a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. So like: Then, there, gently, slowly, and a lot more. Are there any specific words that you need to know are adverbs or not?

A lot of the time or most of the time it ends in ly