Lynn Hansen, a good friend at WesTech Engineering, asked us to write a tip on using the prefixes un- and non- as in uncaring and nonessential.
We’d love to.
Unfortunately, we can’t. We have no answer. The prefixes are too inconsistent. One source put it this way:
It is not possible to predict whether the negative prefix un-, in-, or dis- is used with a particular word. The correct form must be learned.
Oh, yeah. How?
There’s only one way. Get a good dictionary (no more than ten years old) and use it. That’s your source. We’re sorry we couldn’t be more helpful.
Un- comes from Old English and has two meanings. It can mean “Not,” as in “uncaring” or “untrue.” It can also mean “Reverse” as in “untie” or “unlock.”
Non- joined the language from Norman French, where it meant “no.” (Parlez vous Français? Non. Nope. Not me.) Nonessential, essentially, means “not essential.”
The two prefixes have an interesting overlap.
Unrevealed means “not made known” or “kept secret.” (“The budget remains unrevealed.”)
Nonrevealed is a religious term which means “not revealed through a prophet or messenger from God.” (“Belief in the Flying Spaghetti Monster is a non-revealed religion.”