4. The non-transitory computer-readable recording medium according to claim 1 , wherein the plurality of pieces of syntax information are information in which a tree structure of a syntax tree indicating relationships between the plurality of words are expressed using a plurality of subtrees.
5. The non-transitory computer-readable recording medium according to claim 4 , the process further comprising assigning a compression code to nesting information indicating a connection relationship between a subtree of a parent and a subtree of a child of the plurality of subtrees, wherein the outputting the plurality of compression codes outputs the plurality of compression codes assigned to the plurality of words, the plurality of pieces of syntax information, and the nesting information.