Lucene weight sorting factor explanation (for future reference)

Tf (t in d ):Term frequency factor for the term (t) in the document (d)-howmany times the term t occurs in the document.

Idf (t ):Inverse document frequency of the term: a measure of how "unique" the term is. Very common terms have a low idf; very rare terms have a high idf.

Boost (t. field in d ):Field and document boost, as set during indexing (see section 2.5). You may use this to statically boost certain fields and certain documentsover others.

LengthNorm (t. field in d ):Normalization value of a field, given the number of terms within thefield. This value is computed during indexing and stored in the indexnorms. Shorter fields (fewer tokens) get a bigger boost from this factor.

Coord (q, d ):Coordination factor, based on the number of query terms thedocument contains. The coordination factor gives an AND-like boost to related ents that contain more of the search terms than other documents.

QueryNorm (q ):Normalization value for a query, given the sum of the squared weights of each of the query terms.