The words ant, aunt sound the same but have different meanings and spellings. Why do ant, aunt sound the same even though they are completely different words?
The answer is simple: ant, aunt are homophones of the English language.
Any of various social insects of the family Formicidae, characteristically having wings only in the males and fertile females and living in colonies that have a complex social organization.
ants in (one's) pants Slang A state of restless impatience: "She's got ants in her pants” ( Bobbie Ann Mason).
The sister of one's father or mother.
The wife of one's uncle.
Used as a form of address for an older woman, especially by children.
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").