13. The system of claim 11 , wherein the subset hierarchical tree is a subset of the lexical database including a hyponym node associated with the first term, a subset of the plurality hyponym nodes associated with other hyponym terms that share the common parent with the first term, and a subset of the plurality of hypernym nodes associated with hypernym terms within the hierarchy between the subset of the plurality of hyponym nodes and the root node.
13. The system of claim 11 , wherein the subset hierarchical tree is a subset of the lexical database including a hyponym node associated with the first term, a subset of the plurality hyponym nodes associated with other hyponym terms that share the common parent with the first term, and a subset of the plurality of hypernym nodes associated with hypernym terms within the hierarchy between the subset of the plurality of hyponym nodes and the root node. 14. The system of claim 13 , wherein calculating probability values for the plurality of other terms in the subset hierarchical tree includes: calculating, by the computer system, on a per-node basis, a probability value for a given node in the subset hierarchical tree based on probability values of immediate child nodes to the given node using a specified scoring function.