The words mind, mined sound the same but have different meanings and spellings. Why do mind, mined sound the same even though they are completely different words?
The answer is simple: mind, mined are homophones of the English language.
The human consciousness that originates in the brain and is manifested especially in thought, perception, emotion, will, memory, and imagination.
The collective conscious and unconscious processes in a sentient organism that direct and influence mental and physical behavior.
The principle of intelligence; the spirit of consciousness regarded as an aspect of reality.
The faculty of thinking, reasoning, and applying knowledge: Follow your mind, not your heart.
Simple past tense and past participle of mine.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.