warning vs lesson

warning and lesson both are nouns.

Word	Noun	Adjective	Verb	Adverb
warning	Yes	Yes	No	No
lesson	Yes	No	No	No

As nouns, lesson is a hyponym of warning; that is, lesson is a word with a more specific, narrower meaning than warning:

warning: cautionary advice about something imminent (especially imminent danger or other unpleasantness)
lesson: punishment intended as a warning to others

Other hyponyms of warning include deterrent example, example, object lesson.

warning (noun)	lesson (noun)
a message informing of danger	a task assigned for individual study
cautionary advice about something imminent (especially imminent danger or other unpleasantness)	a unit of instruction
notification of something, usually in advance	punishment intended as a warning to others
	the significance of a story or event

warning (adjective)	lesson (adjective)
serving to warn