watch vs ensure

watch is a noun but ensure is not a noun.

Word	Noun	Adjective	Verb	Adverb
watch	Yes	No	Yes	No
ensure	No	No	Yes	No

watch (noun)	ensure (noun)
a purposeful surveillance to guard or observe
the rite of staying awake for devotional purposes (especially on the eve of a religious festival)
a small portable timepiece
a person employed to keep watch for some anticipated event
a period of time (4 or 2 hours) during which some of a ship's crew are on duty
the period during which someone (especially a guard) is on duty

watch (verb)	ensure (verb)
find out, learn, or determine with certainty, usually by making an inquiry or other effort	be careful or certain to do something; make certain of something
look attentively	make certain of
be vigilant, be on the lookout or be careful
observe without intervening
observe or determine by looking
see or watch
follow with the eyes or the mind