9. The encoding apparatus according to claim 6 , wherein the plurality of pieces of syntax information are information in which a tree structure of a syntax tree indicating a relationship between the plurality of words is expressed using a plurality of subtrees.
9. The encoding apparatus according to claim 6 , wherein the plurality of pieces of syntax information are information in which a tree structure of a syntax tree indicating a relationship between the plurality of words is expressed using a plurality of subtrees. 10. The encoding apparatus according to claim 9 , wherein the processor further assigns 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, and outputs the plurality of compression codes assigned to the plurality of words, the plurality of pieces of syntax information, and the nesting information.