The words hoar, whore sound the same but have different meanings and spellings. Why do hoar, whore sound the same even though they are completely different words?
The answer is simple: hoar, whore are homophones of the English language.
Hoary.
Hoarfrost.
A prostitute.
A person considered sexually promiscuous.
A person considered as having compromised principles for personal gain.
To associate or have sexual relations with prostitutes or a prostitute.
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.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").