defend vs keep

defend is not a noun while keep is a noun.

Word	Noun	Adjective	Verb	Adverb
defend	No	No	Yes	No
keep	Yes	No	Yes	No

As verbs, keep is a hypernym of defend; that is, keep is a word with a broader meaning than defend:

defend: be on the defensive; act against an attack
keep: stop (someone or something) from doing something or being in a certain state

Other hypernyms of defend include prevent.

defend (noun)	keep (noun)
	the main tower within the walls of a medieval castle or fortress
	a cell in a jail or prison
	the financial means whereby one lives

defend (verb)	keep (verb)
argue or speak in defense of	prevent (food) from rotting
state or assert	prevent the action or expression of
be on the defensive; act against an attack	stick to correctly or closely
protect against a challenge or attack	maintain by writing regular records
protect or fight for as a champion	supply with necessities and support
fight against or resist strongly	hold and prevent from leaving
be the defense counsel for someone in a trial	retain possession of
	look after; be the keeper of; have charge of
	retain rights to
	maintain for use and service
	have as a supply
	store or keep customarily
	stop (someone or something) from doing something or being in a certain state
	allow to remain in a place or position or maintain a property or feature
	conform one's action or practice to
	behave as expected during of holidays or rites
	cause to continue in a certain state, position, or activity
	supply with room and board
	maintain in safety from injury, harm, or danger
	fail to spoil or rot
	continue a certain state, condition, or activity
	to rear