Sifa. "A certain white boy wrote the exam yesterday." The word that was described as an adjective is sifa.

In English, the sentence would be:

"A certain white boy wrote the exam yesterday."

The word "sifa" means "adjective" or "descriptive word", used to describe a noun or pronoun. In this sentence, "fari" (meaning "white") is an adjective used to describe the noun "yaro" (meaning "boy").