The words vaper, vapor sound the same but have different meanings and spellings. Why do vaper, vapor sound the same even though they are completely different words?
The answer is simple: vaper, vapor are homophones of the English language.
A "<xref>smoker</xref>" of <xref>electronic cigarettes</xref>.
To bully; hector.
To fill or cover with vapor.
The gaseous state of a substance that is liquid or solid at room temperature.
A faintly visible suspension of fine particles of matter in the air, as mist, fumes, or smoke.
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License., from The Century Dictionary., from The American Heritage® Dictionary of the English Language, 5th 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").