= N =

Narrower term (NT)

In the hierarchy of a thesaurus, relationship between a term and a more specific term

NEAR

Physician NEAR relationship retrieves records that contain the words in the same field

E.g. both words  in the Title; in the abstract, and so on

Source : OVID help. Available form: http://www.ovid.com/site/help/documentation/ospb/en/syntax.htm#operators

NOT

The NOT operator lets you retrieve records that contain your first term but exclude the second term. In this way, you can restrict the scope of your results. For example, the search health reform not health maintenance organizations retrieves only those records that contain the term health reform but exclude the term health maintenance organizations.

Source : OVID help. Available form: http://www.ovid.com/site/help/documentation/ospb/en/syntax.htm#operators

Image source : http://en.wikipedia.org/wiki/File:LogicGates.svg [visited 2010-09-15]