The words savior, saviour sound the same but have different meanings and spellings. Why do savior, saviour sound the same even though they are completely different words?
The answer is simple: savior, saviour are homophones of the English language.
A person who rescues another from harm, danger, or loss.
Chiefly British Variant of savior.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.