Technically it is called an "article" - it establishes "definiteness" of a noun.
It indicates a specific individual, example or set within a group of things or concepts, for example the red truck versus just any old red truck, which is a red truck.
"The" is a definite article, a determiner. Some grammar books include determiners as types of adjectives.
To be safe, you can simply classify it as a definite article.
Adjective
Cautious IS an adjective. An adjective is an action!
The word "it" is not an adjective (it is a pronoun). A word is an adjective if it modifies (defines, characterizes) a noun or pronoun. The big tent - big is an adjective He is tall - tall is an adjective This key - this (while arguably called a determiner) is a demonstrative adjective
Severe is an adjective.
Hard is an adjective.
adjective
No, it is a verb or a noun (to go around, to surround; a round shape). The adjective form is circular.
It is an adjective.It is a an adjective.
No, it is not an adjective. Differently is an adverb.The adjective would be different.
No. It is not an adjective. An adjective describes something.
Cautious IS an adjective. An adjective is an action!
No, it is an adverb. The adjective is clumsy.
It can be. "Ideal" is an adjective and a noun.
It is not an adjective. It is a noun based on the adjective unfit.
Yes, it is an adjective.
No it's not a adjective, an adjective is a describing word.
adjective
No, it is not an adjective; it is an adverb. The adjective form is "awkward."