8. A machine translation method, implemented using a computer, comprising: preparing a storage unit configured to store a plurality of interpretation data items each including a first expression element representing a first expression of a first language, an interpretation word set element including the first expression, and a second expression element representing a second expression of a second language, wherein the first expression is to be translated into the second expression, and the first expression and the second expression are included in a category; acquiring, by the computer, a predetermined expression of the first language, the predetermined expression being included in a structure of a to-be-translated document, wherein words or sentences are arranged regularly in the structure; acquiring, by the computer, a first word set element including the predetermined expression and one or more expressions having equivalent positional relationship to the predetermined expression in the structure; detecting, by the computer, a subset from the plurality of interpretation data items, each of the subset including an expression element representing the predetermined expression and one or more word set elements; performing, by the computer, matching between the first word set element and each of the one or more word set elements of the detected subset based on at least one of a number and an order of expressions of the first word set element; selecting, by the computer, from the detected subset, an interpretation data item according to the matching; and translating, by the computer, the predetermined expression into the second language, using the selected interpretation data item.
13. The method according to claim 8 , wherein the first word set element contains data representing a chapter/section structure of the to-be-translated document, and a plurality of expressions in the first word set element are titles of chapters and titles of sections.