The words bach, batch sound the same but have different meanings and spellings. Why do bach, batch sound the same even though they are completely different words?
The answer is simple: bach, batch are homophones of the English language.
To live alone and keep house as a bachelor.
bach it To bach.
An amount produced at one baking: a batch of cookies.
A quantity required for or produced as the result of one operation: made a batch of cookie dough; mixed a batch of cement.
A group of persons or things: a batch of tourists; a whole new batch of problems.
Computer Science A set of data or jobs to be processed in a single program run.
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").