Prefixes That Mean Not: UN-, NON-, DIS-, IN-

Recognize the four most common negative prefixes and the shades of meaning they carry.

Four prefixes do most of English's 'not' work, and each has its own flavor. Un- is the most common and means not or the opposite of: unfair, unlock. Non- means simply not, without much emotion, and often appears in technical words: nonfiction, nonstop, nonliving. Dis- means not or apart, and often suggests reversing or removing: disagree, disconnect, distrust. In- means not and changes to im-, il-, or ir- before certain letters: invisible, impatient, illegal, irregular. Shades matter.

'Unscientific' suggests something is done badly; 'nonscientific' simply means outside science. A poem is nonscientific, but a careless experiment is unscientific. Likewise, 'disinterested' means fair and not taking sides, while 'uninterested' means bored. When you meet a negative prefix, do not stop at 'not'. Ask what kind of not: neutral, reversed, removed, or critical. That question often reveals the author's attitude.

• 1UN-, NON-, DIS-, and IN- all mean not.
• 2NON- is neutral; UN- can sound critical; DIS- often reverses.
• 3Disinterested (fair) is not the same as uninterested (bored).