Both 'favorable' and 'favourable' are correct spellings of the same word, with 'favorable' being the American English spelling and 'favourable' being the British English spelling. The choice between the two depends on the English variant you are using.

The same spelling difference applies to the adjective favourable or favorable and the noun or adjective favourite or favorite. In British English, “favourable” and “favourite” are correct. In American English, “favorable” and “favorite” are correct.

The same spelling distinction carries over to the related words ‘ favourite/favorite’ (meaning ‘preferred above all others’) and ‘favourable/favorable’ (meaning ‘advantageous’ or ‘ complimentary’). In UK English, ‘favourite’ and ‘favourable’ (with a ‘u’) are standard. In US English, ‘favorite’ and ‘favorable’ (with no ‘u’) are correct.

In UK English, “favour” (with a “u”) is the correct spelling. In US English, “favor” (with no “u”) is standard.

Favourable is a alternative form of favorable. As adjectives the difference between favorable and favourable is that favorable is pleasing, encouraging or approving while favourable is pleasing, encouraging or approving.