Number of Terms

The Number of Terms (or Nterms) module ranks matches according to how many query terms they match.

For example, in a three-word query, results that match all three words will be ranked above results that match only two, which will be ranked above results that match only one, which will be ranked above results that had no matches.

With multiple term searches, Nterms only ranks the terms in the field with the most existence of the term. For example, assume that a search is made for 5 terms (a, b, c, d, and e) and you have a record with two fields:

Field 1: a b c
Field 2: d e

This record is ranked as if it matched three terms, the maximum number that matched in any single field.

Note the following about Nterms:

The Nterms module is only applicable to search modes where results can vary in how many query terms they match. These include Any, Partial, Any, and AllPartial. For details on these search modes, see Using Search Modes.
Nterms treats all matches the same, whether or not they are due to query expansion.