maintenance vs maintain

maintenance is a noun but maintain is not a noun.

Word	Noun	Adjective	Verb	Adverb
maintenance	Yes	No	No	No
maintain	No	No	Yes	No

maintenance (noun)	maintain (noun)
activity involved in maintaining something in good working order
the act of sustaining life by food or providing a means of subsistence
the unauthorized interference in a legal action by a person having no interest in it (as by helping one party with money or otherwise to continue the action) so as to obstruct justice or promote unnecessary litigation or unsettle the peace of the community
means of maintenance of a family or group
court-ordered support paid by one spouse to another after they are separated

maintenance (verb)	maintain (verb)
	stick to correctly or closely
	state categorically
	state or assert
	support against an opponent
	maintain by writing regular records
	supply with necessities and support
	keep in safety and protect from harm, decay, loss, or destruction
	have and exercise
	maintain for use and service
	cause to continue in a certain state, position, or activity