advice vs admonition

advice and admonition both are nouns.

Word	Noun	Adjective	Verb	Adverb
advice	Yes	No	No	No
admonition	Yes	No	No	No

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

advice: a proposal for an appropriate course of action
admonition: cautionary advice about something imminent (especially imminent danger or other unpleasantness)

Other hyponyms of advice include recommendation, indication, monition, warning, word of advice.

advice (noun)	admonition (noun)
a proposal for an appropriate course of action	a firm rebuke
	cautionary advice about something imminent (especially imminent danger or other unpleasantness)