The words fort, forte sound the same but have different meanings and spellings. Why do fort, forte sound the same even though they are completely different words?
The answer is simple: fort, forte are homophones of the English language.
A fortified place or position stationed with troops.
A permanent army post.
Something in which a person excels.
The strong part of a sword blade, between the middle and the hilt.
In a loud, forceful manner. Used chiefly as a direction.
A note, passage, or chord played forte.
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").