The words forego, forgo sound the same but have different meanings and spellings. Why do forego, forgo sound the same even though they are completely different words?
The answer is simple: forego, forgo are homophones of the English language.
To precede, as in time or place.
Variant of forgo.
To abstain from; relinquish: unwilling to forgo dessert.
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.