The words aural, oral sound the same but have different meanings and spellings. Why do aural, oral sound the same even though they are completely different words?
The answer is simple: aural, oral are homophones of the English language.
Of, relating to, or perceived by the ear.
Characterized by or relating to an aura.
Spoken rather than written. See Usage Note at verbal.
Of or relating to the mouth: oral surgery.
Used in or taken through the mouth: an oral thermometer; an oral vaccine.
Consisting of or using speech: oral instruction.
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.