The words caudal, caudle sound the same but have different meanings and spellings. Why do caudal, caudle sound the same even though they are completely different words?
The answer is simple: caudal, caudle are homophones of the English language.
Of, at, or near the tail or hind parts; posterior: the caudal fin of a fish.
Situated beneath or on the underside; inferior.
Anatomy Similar to a tail in form or function.
A warm drink consisting of wine or ale mixed with sugar, eggs, bread, and various spices, sometimes given to ill persons.
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").