The words ade, aid, aide sound the same but have different meanings and spellings. Why do ade, aid, aide sound the same even though they are completely different words?
The answer is simple: ade, aid, aide are homophones of the English language.
A suffix of nouns of French or other Romance origin, as accolade, ambuscade, brigade, cannonade, lemonade, etc., or of (a few) English nouns formed on the same model, as blockade, orangeade.
A suffix of nouns of Spanish or Italian origin (originally masculine form of preceding), as brocade, renegade, etc. It also appears in the Spanish form -ado, as in renegado, desperado.
A suffix of Greek origin, now usually -ad, as in decade (sometimes decad), nomade (usually nomad, like monad, triad, etc.).
A drink of the lemonade or orangeade class.
To help or furnish with help, support, or relief. See Synonyms at help.
The act or result of helping; assistance.
An assistant or helper.
A device that assists: visual aids such as slides.
An assistant; a helper: a nurse's aide. See Synonyms at assistant.
Definitions from The Century Dictionary and Cyclopedia, 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").