The word "boy" is a noun. A boy is a person.
Adjective
Boys is a noun. It's the plural form of boy.
It's a pronoun.
"Little" is an adjective, describing the boy. "Boy" is a noun, referring to a young male.
the subject
PREPOSITION
third person singular verb
Conjunction
Comes is a verb in that sentence.
Trace is a verb and a noun.Verb: The boy traced the picture.Noun: The ship disappeared without a trace.
"Unusual" is used as an adjective. e.g. The unusual boy stuttered as he spoke. "unusual" is modifying "boy". Only adjectives modify nouns and pronouns.
The part of speech for this particular word is a noun.