Endeavor and endeavour are the same word, meaning a determined attempt to achieve something, or to try hard to do something. Endeavor is the American spelling, endeavour the British one. If you are writing for a UK audience, use endeavour, as in we shall endeavour to keep you informed.
The core difference
They share the same meaning; endeavor is American English and endeavour is British English.
- endeavor — American spelling: Starting the charity was a personal endeavor she was proud of.
- endeavour — British spelling: The expedition was a remarkable endeavour of human willpower.
How to tell them apart
Both spellings cover the same noun sense, a serious attempt at something difficult, and the same verb sense, to try hard, as in we will endeavor/endeavour to reply within 24 hours. The word traces back to Middle English, built from putting oneself in duty, related to the French devoir.
The confusion tends to appear in formal or business writing, where British firms often keep the phrase we shall endeavour to, while American companies write we will endeavor to. Keep the spelling consistent with the rest of your document's regional style.
