How do you spell perness?

I'm not completely sure of the Word you want; the letters "perness" does not spell any known Word.

The closest Word I can find based on pronunciation of the letters and order you provided is pernicious which means something that has the capacity to cause serious injury, harm or death. It also means deadly. For example, pernicious anemia is one condition marked by low red blood cells which are needed to carry hemoglobin which carries oxygen.

I have included a link for a really helpful website tool where you can type in any Word (even misspelled Words) and based on pronunciation of the letters, the software will tell you possible Words. If you run the cursor over each possible Word, the software will "speak" that Word so you can hear it. It's quite helpful if you are unsure about how to spell a Word.