1. The right mouse button was long treated as nonexistent by Microsoft and many others. Only a few brave programmers connected actions to the right mouse button, and these actions were considered to be extra, optional, or advanced functions.
微软和其他许多公司曾经长期对鼠标右键视而不见,只有少数勇敢的程序员将一些行为与右键关联起来。 这些行为被看做是额外、备选或高级的功能。

-- 来源 -- About Face 3交互设计精髓

2. It is optional with you.
悉听尊便。

-- 来源 -- 英汉 - 辞典例句

3. A 4-speed automatic transmission is optional.
四段自动变速器是可自由选择的。

-- 来源 -- 英汉 - 辞典例句

4. Contributions are purely optional.
捐献完全是随意 [出于自愿] 的。

-- 来源 -- 英汉 - 辞典例句

5. If it is difficult to state definitely one or several ports, optional ports can be adopted.
假如难以明确写出一个或几个港口,就可以采用选择港这个办法。

-- 来源 -- 英汉 - 辞典例句

6. Under some constraint conditions, a procedure to get the optional position of connected objects.
在某些约束条件下,获得相连物体最佳位置的过程。

-- 来源 -- 英汉 - 辞典例句

7. The Format menu is one of the weakest of the optional menus because it deals almost exclusively with properties of visual objects and not functions.
格式菜单是最弱的选项菜单之一,因为它几乎专门用于处理可视对象的性质,而不是功能。

-- 来源 -- About Face 3交互设计精髓

8. The following menus are commonly used, but considered optional in most style guides. An application of moderate complexity is likely to make use of at least some of these menus.
以下各种菜单是十分常用的,但在多数风格指南中都把它们当做可选菜单,一个中度复杂的应用程序至少要用到其中的一部分。

-- 来源 -- About Face 3交互设计精髓

9. Mnemonics are not optional.
访问键不是可有可无的,而是必须要有的。

-- 来源 -- About Face 3交互设计精髓

10. Critical to the effectiveness of a versioning facility is the behavior of the “revert” command. It should provide a list of the available saved versions of the document in question, along with some information about each one, such as the time and day it was recorded, the name of the person who recorded it, the size, and some optional user-entered notes.
“恢复”命令对于保证保存历史版本功能的有效性是非常关键的,它应该提供一个以往各个已保存版本的列表,以及每个版本的相关信息,比如保存的时间日期、上次保存者的姓名、文件大小,以及其他和用户有关的信息。

-- 来源 -- About Face 3交互设计精髓