optional

英 [ˈɒpʃənl]

美 [ˈɑːpʃənl]

adj.  可选择的; 选修的

高考CET4CET6考研TOEFLIELTSGRETEM4TEM8化学

Collins.1 / BNC.5815 / COCA.5692

牛津词典

adj.

• 可选择的；选修的
  that you can choose to do or have if you want to
  1. Certain courses are compulsory, others are optional.
     某些课程是必修的，其他是选修的。
  2. This model comes with a number of optional extras (= things you can choose to have but which you will have to pay extra for) .
     这一型号有一系列可供选择的附件，价格另计。

柯林斯词典

• ADJ 可选择的；非强制的
  If something isoptional, you can choose whether or not you do it or have it.
  1. A holiday isn't an optional extra. In this stressful, frantic world it's a must...
     休假并非可有可无。在这个紧张而忙碌的世界，它是必不可少的。
  2. Sex education is a sensitive area for some parents, and thus it should remain optional.
     性教育对某些家长而言是个敏感领域，因此应该保持其非强制性。

英英释义

adj

• possible but not necessary

双语例句

• Note that both the dependencies and the instructions are optional; only the target and the colon are required.
  请注意依赖性和指令都是可选的；只有目标和冒号才是必须的。
• An activity can also have optional and required inputs and attributes, as defined by the activity's creator.
  活动还可以拥有可选和必要输入和属性，这由活动创建者定义。
• This contains a list of mandatory and optional fields.
  它包含一个强制性和非强制性命令的列表。
• The square brackets ( [ and]) enclose optional parameters.
  方括号（[和]）中的是可选参数。
• Optional and named arguments can be used not only with methods but also with indexers and constructors.
  可选参数和命名参数不仅可以用在方法调用中，还可以用在索引器和构造器中。
• Actions and predicate are optional.
  动作和断言是可选的。
• You pass the before method an optional symbol and a code block.
  您向before方法传递一个可选的标志和一个代码块。
• The cycles are periodic and optional.
  循环是阶段性和可选择的。
• Above the communication protocols are the optional file attachment and security layers that are implemented with MIME.
  通信协议的上面是可选的文件附件和安全层，用MIME实现。
• Our attendance at graduation is optional.
  毕业典礼可以自愿参加。