It's important to understand the distinction between formal and informal language.

distinction 是名词，来自动词 distinguish（区分、辨别），意思是"区别、差异"。 formal 指"正式的"，informal 指"非正式的"，两者形成对比关系。 distinction between formal and informal language 指"正式语言和非正式语言之间的区别"。