Double Negative

Double negative is one of the common problems in writing especially for non-native speakers. It occurs when two negative words are used in a single clause. It is produced by combining a negative word with a negative pronoun, negative adverb, and another negative word.

[1] With a negative pronoun

The negative pronouns are none, nothing, nowhere, nobody, no one, neither, etc. Look at these examples,
- I didn't meet nobody there. (Double negative)
→ I met nobody there.
- He didn't do nothing.  (Double negative)
→ He did nothing.  

[2] With negative words

The negative adverbs are are not, hardly, scarcely, never, barely, seldom, etc. Look at these examples,
- I couldn’t hardly wait to get to the party. (Double negative)
→ I could hardly wait to get to the party.
- I did not barely understand what you were saying. (Double negative)
→ I barely understood what you were saying.

[3] With a negative words 

Look at the examples,
- The city is not unattractive. (Double negative)
→ The city is unattractive. 
- She is not unhappy. (Double negative)
→ She is unhappy.

Why do you need to avoid double negative?

You need to know that when you use two negative words in a sentence, the meaning will be positive. For examples,
- She is not unhappy. = She is happy.
- He didn't do nothing. = He did something.