stumble vs err

stumble is a noun but err is not a noun.

Word	Noun	Adjective	Verb	Adverb
stumble	Yes	No	Yes	No
err	No	No	Yes	No

As verbs, err is a hypernym of stumble; that is, err is a word with a broader meaning than stumble:

Other hypernyms of stumble include mistake, slip.

stumble (noun)	err (noun)
an unsteady uneven gait
an unintentional but embarrassing blunder

stumble (verb)	err (verb)
make an error	to make a mistake or be incorrect
miss a step and fall or nearly fall	wander from a direct course or at random
walk unsteadily, tripping repeatedly
encounter by chance