optional
美 [ˈɑpʃən(ə)l] 
英 [ˈɒpʃ(ə)nəl]
- adj.可选择的；选修的
- n.〈美〉选修科
- 网络非强制的；可选的；可以任选的
反义词
英汉双解
1. | 可选择的；选修的that you can choose to do or have if you want to |
| Certain courses are compulsory; others are optional. 有些课程是必修的，其他是选修的。 |
| 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。 |
英汉解释
英英解释
例句
The new lock-in offer is part of a series of optional add-ons airlines have been rolling out in an effort to increase revenue.
这个全新的票价锁服务是其中一个航空公司为了增加盈利而推出的一系列附加服务选项。
The owner of each end point decides how much optional information to provide with the endpoint URL.
每个端点的所有者决定端点URL提供多少可选信息。
After a join hint is specified, the INNER keyword is no longer optional and must be explicitly stated for an INNER JOIN to be performed.
指定联接提示后，要执行INNERJOIN时，INNER关键字不再为可选，而必须显式说明。
In some smaller restaurants with fewer people dining, like the case of a couple of diners, the measure's adoption could be optional.
有一些小餐馆就餐人数比较少，比如一两个人、两三个人，可以有一些随意的情况。
In fact, for one-to-one associations that are optional on both end, the code generated by the wizard is all we need.
实际上，对于两端都可选的一对一关联，只需要向导生成的代码就够了。
A few days before a big social-science exam, the instructor informed us that he would hold an optional review session the next day.
在一场大型社会科学考试前几天，导师通知我们第二天他将会给我们上一节选修复习课。
This optional view appears at the bottom edge of a screen and contains segments that activate different modes in the application.
这个可选控件出现于应用程序的页面底部，用于切换程序的不同状态。
If you don't want the active rule to be reevaluated, you should include the rule's optional no-loop attribute and give it a value of true.
如果不希望这种情况发生，则应该包括rule的可选no-loop属性并将其赋值为true。
An optional step at this point may be to create a link aggregation device, commonly referred to as the LNAGG device.
（这里有一个可选步骤——创建一个链路聚合设备，通常称为LNAGG设备）。
Finally, while a dangling lure is optional, being hungry, Dr. Wilson says, at least metaphorically, "probably helps quite a bit. "
最后，虽然悬挂的诱饵可有可无，威尔逊说，但至少是从喻义上来说，饥饿状态“可能会很有帮助。”
The filters can be supplied either as individual filters or as ready-to-install offline units complete with optional motor and pump units.
该过滤器可以提供不论作为个别的过滤器或可直接安装可选的电机和水泵机组完全脱机单位。
Beside this, we must take account of the fact that in China breathing seems to be optional.
除此之外，我们还要考虑到这样一个事实：在中国，新鲜空气是可有可无的。
This update is optional and simply provides a more up-to-date definition of messages that are considered to be junk or not junk.
此更新是一可选件，只提供用于判断邮件是否为垃圾邮件的最新定义。
"Moving three evictions , optional neighbouring states, " the importance of education has always been a traditional Chinese virtue.
“孟母三迁，择邻而居”，重视教育一直是中国的一个传统美德。
That noted, it seems to me that optional tips are an attractive way of doing business.
鉴于此，我觉得随意小费制是个有吸引力的办法。
It has much more sharply tapered edges, and a new, optional, white color adds to the sense of lightness.
它的边缘削得更厉害，新增的、可选的白颜色使它看起来更轻。
sed takes a script of any number of commands followed by an optional input filespec; by default, it reads standard input.
sed接受包含任何数量命令的脚本，后面跟着可选的指定输入文件的选项；缺省情况下，它读取标准输入。
The difference is subtle: running the test without the optional flag helps you understand the total time, even in the case of a failure.
区别很微妙：在一个失败的样例中，不带可选标志运行测试可以帮您了解运行总时间。
The structure and validity of the MDMP must also be examined as the metric to which optional decision-making processes are compared.
军事决策程序MDMP的结构和有效性同样要作为可选的决策程序相对比的衡量标准来检验。
They had a special offer for a Sony VAIO, which had a very nice large screen and space for an optional second battery.
他们有一个SonyVAIO的特别提供，它有一个非常好的大萤幕以及额外的第二颗电池的空间。
The broker is optional in the base pattern but is often a critical piece in enterprise systems.
在基本模式中代理是可选的但是在企业系统中经常是关键性部件。
The terms included in DCMI are divided into a minimal set of base elements and an optional collection of refinements to these base elements.
DCMI中的术语被划分成最小化的基本元素集和对这些基本元素细化的可选集。
The position of the front wheel turning table(optional part )is adjustable so that the side slide plate can be fit for more cars.
前轮转角（选购件）位置可调，加长双级后轮滑板，适合各种车形。
She said this was "maybe the second or third time" her employer had an optional snow day in the last five years.
她说“这可能是我遇到过的第二或者第三次因为大雪天而休假了。”单位在过去五年好像有问过一次类似的选择题。
Implementations must support texture sizes at least up to 256, which is one of the optional properties in M3G.
部件必须至少支持256的纹理大小，这是M3G的一个可选属性。
Optional: A "what if? " alternative can be created (a second such picture, sometimes referred to as a "future state" Value Stream Map).
可选的：可以创建一个“如果这样做会怎样”的选择（第二个这样的图片，有时也叫做“未来状态”价值流图）。
"Optional" fees are being applied to elements that used to be included in base prices. Some are easy to avoid, others not so easy.
“任选”费用被应用到曾经包含在基础价格中的部分，有的容易避免，有的却不能。
The name of the element to be created is specified by a required name attribute and an optional namespace attribute.
要创建的元素的名称由必选的name属性和可选的namespace属性指定。
While category and series groups are optional, at least one of these groups is required to display meaningful data in the chart.
虽然类别组和序列组是可选的，但是必须至少选择其中一种，才能在图表中显示有意义的数据。
All of the additional parameters are optional so you specify only as much information as you want.
所有其它参数都是可选的，因此您只指定您想要的信息便可。
Another optional argument allows you to delete only e-mails of a certain type, specified as the sent_status argument.
另一个可选参数允许您仅删除作为sent_status参数指定的特定类型的电子邮件。
Until recently, many students saw these optional courses to be just a source of extra credits required for graduation.
直到最近，很多学生还认为选修课只是一种修够毕业所需额外学分的途径。
The company is also going to continue with an optional programme that lets players use their real identities in a game if they so wish.
该公司还将继续推行一项选择性计划，让那些希望使用真实身份的玩家在游戏中使用真实身份。
Commonly referred to as "the nudist capital of America" , Pasco boasts dozens of clothes-free and clothing-optional communities.
帕斯科常被称为“美国裸体主义者的首都”，当地人以其数十个无衣社区或穿脱自便的社区而自豪。
The index tablespace is optional, so the system tablespace can be used for indexing purpose, instead of the index tablespace.
索引表空间是可选的，可以使用系统表空间存储索引。
Ask why she can ask this, Yang flower dare not say what the past, can only optional bye reason, in a hurry to leave.
可中问她为何问这个，杨朵不敢说出往事，只能随意掰了个理由，匆忙离去。
About half way through the test i read the next question and realised none of the optional answers were correct : |.
在考试进行到一半的时候，我正读题呢，突然就意识到那道题没一个选项是正确的！
God would not have made marital intimacy so intensely pleasurable if it were merely an optional ingredient in our marriage relationships.
如果婚姻的亲密度只是我们婚姻关系中的一个可选成分，那么上帝也不会让夫妻渴望亲密的程度如此的强烈。
A transition is reflected by an arc with annotations for the event, an optional condition, and the action to be performed.
中，转移是通过带有事件注释的弧线、可选的条件以及将要执行的动作来反映的。
When starting a bet the users have to pay an optional amount of money into a pool.
当开始打赌时，用户必须支付一个可选数量的钱进入游泳池。
