irritation vs annoying

irritation and annoying both are nouns.

Word	Noun	Adjective	Verb	Adverb
irritation	Yes	No	No	No
annoying	Yes	Yes	No	No

As nouns, irritation and annoying are synonyms defined as:

Other synonyms of irritation include annoyance, vexation.

irritation (noun)	annoying (noun)
unfriendly behavior that causes anger or resentment	the act of troubling or annoying someone
the act of troubling or annoying someone
an uncomfortable feeling of mental painfulness or distress
a sudden outburst of anger
the psychological state of being irritated or annoyed
the neural or electrical arousal of an organ or muscle or gland
(pathology) abnormal sensitivity to stimulation

irritation (adjective)	annoying (adjective)
	causing irritation or annoyance