theory vs theorise

theory is a noun but theorise is not a noun.

Word	Noun	Adjective	Verb	Adverb
theory	Yes	No	No	No
theorise	No	No	Yes	No

theory (noun)	theorise (noun)
a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena
a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena
a belief that can guide behavior

theory (verb)	theorise (verb)
	to believe especially on uncertain or tentative grounds