irritate vs irritation

irritate is not a noun while irritation is a noun.

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

irritate (noun)	irritation (noun)
	unfriendly behavior that causes anger or resentment
	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

irritate (verb)	irritation (verb)
excite to an abnormal condition, or chafe or inflame
excite to some characteristic action or condition, such as motion, contraction, or nervous impulse, by the application of a stimulus
cause annoyance in; disturb, especially by minor irritations