Either/or and neither/nor

Either/or and neither/nor - beware double negatives

'Neither' is used with 'nor'. (This pairing plays a negative role in the sentence - explained below.)

'Either' is used with 'or'. (Sometimes, the word 'either' is omitted.)

Either/Or and Neither/Nor

The pairings either/or and neither/nor can be used to group two people or things. Although not a major grammatical error, the grouping of more than two things is frowned upon by some style conventions.

Examples:

 Neither the forwards nor the scrumhalf, all of whom were within 10 metres
of the tackle, nor the crowd appealed for a foul.  (three things grouped)

 I could neither laugh nor cry. 

 Either the clerk or the secretary has the keys to the Rover. 
(Note: "has" is correct / "have" would be wrong / See the lesson Either/Or Singular or Plural?)

 The clerk or the secretary has the keys to the Rover.  ('Either' left out)

 He did not find the key either on or under the mat. 

Beware Double Negative

The pairing neither/nor plays a negative role in the sentence.  Be careful not to use a double negative.

 Adam did not find the key neither on nor under the mat. 
(This is a double negative.)

 He did not mention neither the flooding nor the landslide. 
(This is a double negative.)

 He mentioned neither the flooding nor the landslide.  

 He did not mention either the flooding or the landslide.