The words stade, staid, stayed sound the same but have different meanings and spellings. Why do stade, staid, stayed sound the same even though they are completely different words?
The answer is simple: stade, staid, stayed are homophones of the English language.
A landing place or wharf.
Characterized by sedate dignity and often a strait-laced sense of propriety; sober. See Synonyms at serious.
Fixed; permanent: "There is nothing settled, nothing staid in this universe” ( Virginia Woolf).
Simple past tense and past participle of stay.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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").