Region subtags are used to specify the variety of a language "as used in" a particular region. They are appropriate when the variety is regional in nature, and can be captured adequately by identifying the countries involved, as when distinguishing British English ("en-GB") from American English ("en-US"). When the difference is one of script or script variety, as for simplified versus traditional Chinese characters, it should be expressed with a script subtag instead of a region subtag; in this example, "zh-Hans" and "zh-Hant" should be used instead of "zh-CN" and "zh-HK".