A stem is the existing form to which a derivational affix can be added. A stem can be a bound root, a free morpheme, or a derived form itself.

• 派生词缀可加在已存在的形式词上形成的一个新词,原来存在的形式词被称为词干。词干可以是粘着词根,自由词素和一个派生词。