The words fainting, feinting sound the same but have different meanings and spellings. Why do fainting, feinting sound the same even though they are completely different words?
The answer is simple: fainting, feinting are homophones of the English language.
An act of collapsing to a state to temporary unconsciousness.
Present participle of faint.
A feigned attack designed to draw defensive action away from an intended target.
A deceptive action calculated to divert attention from one's real purpose. See Synonyms at wile.
To make a feint.
To deceive with a feint.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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").