annoyance vs red flag

annoyance and red flag both are nouns.

Word	Noun	Adjective	Verb	Adverb
annoyance	Yes	No	No	No
red flag	Yes	No	No	No

As nouns, red flag is a hyponym of annoyance; that is, red flag is a word with a more specific, narrower meaning than annoyance:

Other hyponyms of annoyance include exasperation.

annoyance (noun)	red flag (noun)
the act of troubling or annoying someone	something that irritates or demands immediate action
something or someone that causes trouble; a source of unhappiness	a flag that serves as a warning signal
anger produced by some annoying irritation	the emblem of socialist revolution
an unpleasant person who is annoying or exasperating
the psychological state of being irritated or annoyed