The words rondeau, rondo sound the same but have different meanings and spellings. Why do rondeau, rondo sound the same even though they are completely different words?
The answer is simple: rondeau, rondo are homophones of the English language.
A lyrical poem of French origin having 13 or sometimes 10 lines with two rhymes throughout and with the opening phrase repeated twice as a refrain.
A medieval French song, either monophonic, as in the songs of the trouvères, or polyphonic in construction.
A musical composition built on the alternation of a principal recurring theme and contrasting episodes.
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").