The words ceding, seeding sound the same but have different meanings and spellings. Why do ceding, seeding sound the same even though they are completely different words?
The answer is simple: ceding, seeding are homophones of the English language.
Present participle of cede.
Present participle of seed.
The arrangement of positions in a tournament
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License 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").