“He is a bonified expert in his field.” “This is a bonified offer.”
Your Literary Life Hacker has seen this spelling everywhere, even in nationally syndicated newspaper columns and published books – but it’s wrong.
The correct term is “bona fide,” from the Latin for “in good faith.” It means genuine, without fraud or deception, or officially authorized. Latin scholars may cringe at this, but its English plural form can also be used as a noun: “I checked her bona fides.”
Fun fact: “Bonify” is a word, but it’s a very archaic word that means “to make something good, especially something that was bad before,” according to the business and technical writing resource WhatIs.com.
Avoid using “bonified” when you mean “bona fide,” and your readers will see you as a bona fide smart writer.