A word used to describe a noun is an adjective; a word used to describe, or modify, a verb or an adjective is an adverb.
Thick is usually an adjective; thickly would be the adverb form. You look at the usage of a word in a sentence to find its "part of speech."
adverb
what part of speech is beneath
i want to know what part of speech is camping
The part of speech is a adjective
Oppose is a verb.
Thick can be an adjective, a noun and an adverb. Adjective: e.g. heavy in build. Noun: The thickest part of something. Adverb: In a thick manner.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath
The part of speech for "unfamiliar" is an adjective.
The part of speech of "came" is a verb.
The part of speech for "twirl" is a verb.
The part of speech for "explicit" is an adjective.
The part of speech for "indefinite" is an adjective.
The part of speech for "lecturer" is a noun.