endeavor vs endeavour

endeavor and endeavour both are nouns.

Word	Noun	Adjective	Verb	Adverb
endeavor	Yes	No	Yes	No
endeavour	Yes	No	Yes	No

As nouns, endeavor and endeavour are synonyms defined as:

endeavor and endeavour: earnest and conscientious activity intended to do or accomplish something

Other synonyms of endeavor include attempt, effort, try.

As nouns, endeavor and endeavour are synonyms defined as:

endeavor and endeavour: a purposeful or industrious undertaking (especially one that requires effort or boldness)

Other synonyms of endeavor include enterprise.

As verbs, endeavor and endeavour are synonyms defined as:

Other synonyms of endeavor include strive.

endeavor (noun)	endeavour (noun)
earnest and conscientious activity intended to do or accomplish something	earnest and conscientious activity intended to do or accomplish something
a purposeful or industrious undertaking (especially one that requires effort or boldness)	a purposeful or industrious undertaking (especially one that requires effort or boldness)

endeavor (verb)	endeavour (verb)
attempt by employing effort	attempt by employing effort