The words con, conn, khan sound the same but have different meanings and spellings. Why do con, conn, khan sound the same even though they are completely different words?
The answer is simple: con, conn, khan are homophones of the English language.
In opposition or disagreement; against: debated the issue pro and con.
An argument or opinion against something.
One who holds an opposing opinion or view.
To study, peruse, or examine carefully.
Nautical Variant of con3.
A ruler, an official, or an important person in India and some central Asian countries.
A medieval ruler of a Mongol, Tartar, or Turkish tribe.
A caravansary in certain Asian countries.
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").