15. A non-transitory computer-readable medium including computer executable instructions, wherein the instructions, when executed by a processor, cause the processor to perform a method comprising: storing, in a storage unit, 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 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 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 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 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, from the detected subset, an interpretation data item according to the matching; and translating the predetermined expression into the second language, using the selected interpretation data item.
16. The non-transitory computer-readable medium according to claim 15 , wherein the storage unit contains, as all or several of the plurality of interpretation data items, a condition used to select an interpretation data item including a word set element corresponding to the first word set element, and the method further includes selecting the interpretation data item including the word set element corresponding to the first word set element, if the detected subset contains the condition and the expression element representing the predetermined expression satisfies the condition.