All subjects are part of speech for they are all nouns.
it depends what word it is it could be any part of speech depending on the sentence
An active verb is required; any other part of speech may be present.
A contraction. I is a noun/subject of a sentence. Am (the 'm) is a verb.
"Say" is a verb.
It is a noun, but it is not the subject of the sentence... it is just part of a prepositional phrase.
it depends what word it is it could be any part of speech depending on the sentence
subject
The subject!
A single word that is the subject of a sentence must be either a noun or a pronoun. However, some phrases and clauses, which are not considered to have parts of speech in themselves, can be the only subject in a sentence.
the subject
In this sentence "it" is used as the subject of an impersonal verb and is therefore a pronoun.
An active verb is required; any other part of speech may be present.
A contraction. I is a noun/subject of a sentence. Am (the 'm) is a verb.
* adjective * modifies the subject of the sentence 'novel'
"Say" is a verb.
The phrase "I was then too young" is a complete sentence comprised of a subject ("I") and a verb ("was"), therefore it is a declarative sentence. It does not represent a single part of speech as it contains multiple elements functioning together.
In the sentence "tomorrow is a mystery," 'tomorrow' is a noun functioning as the subject of the sentence.