The words for, fore, four sound the same but have different meanings and spellings. Why do for, fore, four sound the same even though they are completely different words?
The answer is simple: for, fore, four are homophones of the English language.
Used to indicate the object, aim, or purpose of an action or activity: trained for the ministry; put the house up for sale; plans to run for senator.
Used to indicate a destination: headed off for town.
Used to indicate the object of a desire, intention, or perception: had a nose for news; eager for success.
Used to indicate the recipient or beneficiary of an action: prepared lunch for us.
The front part.
Something that is located at or toward the front.
Located at or toward the front; forward.
Earlier in order of occurrence; former.
The cardinal number equal to 3 + 1.
The fourth in a set or sequence.
Something having four parts, units, or members, such as a musical quartet or a four-cylinder engine.
all fours All four limbs of an animal or person: a baby crawling on all fours.
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").