8. The method of claim 7 , wherein each node of the probability tree is associated with a probability value and calculating the frequency score of the suffix is based on the probability value associated with the node corresponding to the one or more words in the suffix.
7. The method of claim 1 , wherein calculating the frequency score of a particular suffix includes using a probability tree having a plurality of nodes, each node corresponding to one or more words of the suffixes, wherein, in the probability tree, a first node is a child of a second node if the one or more words corresponding to the second node partially overlap the one or more words corresponding to the first node.