之前在很多地方都能見到I18N，特別是open source裡面。I18N就是Internationalization的縮寫，其原因是I和n之間一共有18個字母。
下面這些地方會需要I18N
Displaying characters for the users' native languages. Inputing characters for the users' native languages. Handling files written in popular encodings that are used for the users' native languages. Using characters from the users' native languages for file names and other items. Printing out characters from the users' native languages. Displaying messages by the program in the users' native languages. Formatting input and output of numbers, dates, money, etc., in a way that obeys customs of the users' native cultures. Classifying and sorting characters, in a way that obey customs of the users' native cultures. Using typesetting and hyphenation rules appropriate for the users' native languages.當然除了I18N還有L10N(localization) 和M17N (multilingualization)，這3個之間有什麼區別呢，舉例說明。
L10N支持2種語言，英文和另外一種語言（例如中文）；
I18N支持多種語言，但是同一時間只能是英文和一種選定的語言，例如英文+中文、英文+德文、英文+韓文等等；
M17N可以在同一時間支持多種語言，例如你可以在一個頁面裡看到中文、英文、德文和韓文。