The words praying, preying sound the same but have different meanings and spellings. Why do praying, preying sound the same even though they are completely different words?
The answer is simple: praying, preying are homophones of the English language.
Of or pertaining to prayer.
An act of saying a prayer.
Present participle of pray.
Present participle of prey.
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.