Prefixes That Mean Not: in-, im-, non-

Recognize in-, im-, and non- as prefixes that turn a word into its opposite.

Several prefixes mean not. 'In' is one: incomplete means not complete, and incorrect means not correct. Before words starting with b, m, or p, 'in' usually changes to 'im', because it is easier to say: impossible, impatient, imperfect. 'Non' also means not, often in science and everyday words: nonfiction means not made up, and nonstop means without stopping.

Be careful: 'in' does not always mean not. In 'inside' and 'indoor', it means in or into. Check the meaning with the sentence. Read: 'It seemed impossible, but the nonstop train arrived on time. ' Impossible means not possible, and nonstop means it did not stop. Both prefixes flip the base word.

• 1in-, im-, and non- can all mean not.
• 2in- becomes im- before b, m, or p.
• 3Watch out: in- can also mean into (indoor).