The words mewl, mule sound the same but have different meanings and spellings. Why do mewl, mule sound the same even though they are completely different words?
The answer is simple: mewl, mule are homophones of the English language.
To cry weakly; whimper.
The sterile hybrid offspring of a male donkey and a female horse, characterized by long ears and a short mane.
A sterile hybrid, as between a canary and other birds or between certain plants.
Informal A stubborn person.
A spinning machine that makes thread or yarn from fibers. Also called spinning mule.
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.