The adjective form of brevity is brief, so yes.
The speech was notable more for its brevity than for its clarity.
As an adjective.
When used in a sentence the word brainy is an adjective. The brainy boy was at the top of his class.
The word "meet" is not an adjective and cannot be used as an adjective.
a word is used to make a sentence whereas an adjective describes a noun (an object)
In the sentence "It was quite late for a telephone call," the word "quite" is an adverb used to modify the adjective "late."
it is a possessive pronoun (but used as an adjective, because it modifies a noun).
There is no adjective in that sentence. The word "fast" is sometimes used as an adjective, but in this sentence it modifies the verb "run," so "fast" is an adverb.
An adjective is a part of speech that is commonly called a "describing" word. An adjective is used to describe a noun in a sentence. For example, in the sentence "The sun set behind the red barn." the adjective is the word "red", and the noun it is describing is the word "barn."
The word "the" is a definite article, used like an adjective.
The word your is an adjective; the pronoun form is yours. The adjective dark is used as an adjective; the word dark is also a noun.
The adjective in that sentence is "beautiful". An adjective is used to desciribe a noun. The noun in the sentence is "gift".