define data command

例句：

1. 1. The company defines its mission statement clearly.
   这家公司清晰地定义了其使命声明。
2. 2.Teachers need to define the concepts before students can understand them.
   教师在学生理解之前需要定义这些概念。
3. 3.The definition of a word is crucial for understanding its usage.
   一个词的定义对于理解它的用法至关重要。