有用的表达用英语表达为：useful expression；
expression：
n.表示;表达;表露;表情;神色;词语;措辞;表达方式
复数： expressions
This expression is used mainly in speech, not in writing.
这种表达主要用于口语，而不是书面语。
The course teaches students to avoid ambiguity and obscurity of expression.
这门课程教学生避免表达上的模棱两可、含混不清。
Try to put a little more expression into it!
尽量注入更多的感情！
Freedom of expression is a basic human right.
言论自由是基本的人权。
The expression in her eyes told me something was wrong.
她的眼神告诉我出事了。
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