17. The system of claim 16 , 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.
18. The system of claim 17 , configured to perform operations comprising: calculating, using the function, the probability value associated with the node corresponding to the one or more words in the suffix based at least in part on child nodes of the node.