The words callous, callus sound the same but have different meanings and spellings. Why do callous, callus sound the same even though they are completely different words?
The answer is simple: callous, callus are homophones of the English language.
Having calluses; toughened: callous skin on the elbow.
Emotionally hardened; unfeeling: a callous indifference to the suffering of others.
To make or become callous.
A localized thickening and enlargement of the horny layer of the skin. Also called callosity.
The hard bony tissue that develops around the ends of a fractured bone during healing.
Botany Undifferentiated tissue that develops on or around an injured or cut plant surface or in tissue culture.
Botany The hardened, sometimes sharp base of the floret of certain grasses.
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.