原子：元素的特征性质保持不变的最小物质单元，也是在不释放带电粒子的情况下物质能够分割的最小单元。

Atom: Smallest unit into which matter can be divided and still retain the characteristic properties of an element.

youdao

如果集合不包含使用指定名称的元素，则该集合保持不变，且不引发异常。

If the collection does not contain an element with the specified name, the collection remains unchanged and no exception is thrown.

youdao

如果集合不包含使用指定名称的元素，则该集合保持不变，且不引发异常。

If the collection does not contain an element with the specified name, the collection remains unchanged and no exception is thrown.

youdao