Use NOT in front of any search expression to reverse its meaning.  This allows you to exclude documents from a search.  Example:

apple sauce and not pear

NOT standing alone can be the start of a search request.  For example, not pear would retrieve all documents that did not contain pear

If NOT is not the first connector in a request, you need to use either AND or OR with NOT:

apple or not pear

not (apple w/5 pear)

The NOT W/ ("not within") operator allows you to search for a word or phrase not in association with another word or phrase.  Example:

apple not w/20 pear

Unlike the W/ operator, NOT W/ is not symmetrical.  That is, apple not w/20 pear is not the same as pear not w/20 apple.  In the apple not w/20 pear request, dtSearch searches for apple and excludes cases where apple is too close to pear.  In the pear not w/20 apple request, dtSearch searches for pear and excludes cases where pear is too close to apple.