An adjective describes something. A person, a place, an idea, anything at all. How you would use it in a sentence is to describe something. For example, in the sentence below, the word friendly is the adjective.
Sally was a friendly girl.
The adjective word friendly, describes what Sally is like.
An adjective describes a noun.
When writing a sentence
An adjective is a word that describes a noun or a verb. An example of a sentence that uses the word "abstract" in a sentence as an adjective would be: It is difficult for children to fully comprehend many abstract ideas.
If a plant is bifoliate, it has two leaves
Terrain is a noun. It would not be used as an adjective, but adjectives could describe the noun terrain.
The adjective in that sentence would be skillfully.
You would have to use the adjective form, which is expeditious. "An expeditious program of renovation allowed the factory to continue its operations."
It was difficult to figure out which were the invited guests and which were not.
by adjective in the sentence
In a sentence.
NO but in the sentence "Use of the word "in" as an adjective is IN these days" the IN is an adjective
The predicate adjective in this sentence would be careful.