The words hart, heart sound the same but have different meanings and spellings. Why do hart, heart sound the same even though they are completely different words?
The answer is simple: hart, heart are homophones of the English language.
A male deer, especially a male red deer over five years old.
Anatomy The chambered muscular organ in vertebrates that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system.
Anatomy A similarly functioning structure in invertebrates.
The area that is the approximate location of the heart in the body; the breast.
The vital center and source of one's being, emotions, and sensibilities.
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.