Do is always a verb either a main verb or an auxiliary verb.
In the sentence "What can you do," the word "do" is a verb. It is used to indicate an action or something that can be done.
"When" is an adverb when it begins a sentence.
In a sentence, the word "action" can function as a noun.
The part of speech for "gliding" is a gerund, which functions as a noun in a sentence.
The part of speech of "correct" in this sentence is an adjective.
The part of speech that answers "what" or "whom" in a sentence is a pronoun. Pronouns are words like "he," "she," "it," "they," "who," and "what" that replace nouns in a sentence.
In a sentence, the word "action" can function as a noun.
it depends what word it is it could be any part of speech depending on the sentence
"When" is an adverb when it begins a sentence.
All subjects are part of speech for they are all nouns.
you
Pronoun
Noun
Him is a pronoun.
a sentence is a part of speech
Why is the beginning of a interrogative sentence.
In the sentence, "Which is his sister?", "which" is an interrogative pronoun.
Noun--however, many words have several possible parts of speech; please submit the Whole Sentence when asking for part of speech--cannot be sure without seeing how it is used in the sentence, as that's what determines the part of speech.