It's a verb.
It's a noun.
noun
"When" is an adverb when it begins a sentence.
it depends what word it is it could be any part of speech depending on the 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 action... described in a sentence. Since any sentence is about news... descriptions... it is considered to be the essence of the sentence proven by it's ability to stand alone without any other part of speech in communication.
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.
All subjects are part of speech for they are all nouns.
you
a sentence is a part of speech