The words pencel, pencil, pensile sound the same but have different meanings and spellings. Why do pencel, pencil, pensile sound the same even though they are completely different words?
The answer is simple: pencel, pencil, pensile are homophones of the English language.
A narrow flag, streamer, or pennon, especially one carried at the top of a lance or spear.
A narrow, generally cylindrical implement for writing, drawing, or marking, consisting of a thin rod of graphite, colored wax, or similar substance encased in wood or held in a mechanical holder.
Something shaped or used like a pencil, especially a narrow medicated or cosmetic stick: an eyebrow pencil.
A style or technique in drawing or delineating.
Descriptive skill: "His characters are drawn with a strong pencil” ( Henry Hallam).
Hanging loosely; suspended: the pensile nest of the Baltimore oriole.
Having or building a hanging nest. Used of birds.
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").