ConstGND (Google Normalized Distance): favors focused and discriminative terms.
JLH score: emphasizes sharp increases in frequency within the subset.
Mutual information: captures all co-occurrence relationships between term and class.
Percentage score: measures the proportion of term occurrences that fall within the subset. Can be overly sensitive to low-frequency terms
Used by Solr for the "relatedness" aggregation
Chi-square: classical statistical test for independence between term and class.