Ruby（3.2） 中使用了下列关键词（也成保留字）：
- ENCODING
- 当前文件的编码。参阅 Encoding
- LINE
- 关键词在当前文件中的行号。
- FILE
- 当前文件路径。
- BEGIN
- 当前文件中最先运行的代码。参阅 miscellaneous syntax
- END
- 当前文件中所有代码运行完之后再运行。参阅 miscellaneous syntax
- alias
- 为两个方法之间创建一个别名（或者其它）。查阅 模块和类语法
- and
- 优先值低于 && 的短路布尔值
and - begin
- 开始一个意外情况处理代码块。查阅 意外语法
- break
- 跳离一个块。查阅 流控制表达式语法
- case
- 开始
case表达式。查阅 流控制表达式语法 - class
- 创建或者打开一个类。查阅 模块和类的语法
- def
- 定义一个方法。查阅 方法语法
- defined?
- 返回一个描述参数的字符串。查阅 miscellaneous syntax
- do
- 开始一个代码块。
- else
case、if和unless表达式中受控条件之外的情况。查阅 流控制表达式- elsif
if表达式的一个替代条件表达方式。查阅 流控制表达式- end
- 代码语法块的结束标志。用于类、模块、方法、意外处理和流控制。
- ensure
- Starts a section of code that is always run when an exception is raised. See exception handling
- false
- 布尔值 false。查阅 字面量1(literal)
- for
- A loop that is similar to using the each method. See control expressions
- if
- Used for if and modifier if statements. See control expressions
- in
- Used to separate the iterable object and iterator variable in a for loop. See control expressions It also serves as a pattern in a case expression. See pattern matching
- module
- Creates or opens a module. See modules and classes syntax
- next
- Skips the rest of the block. See control expressions
- nil
- A false value usually indicating “no value” or “unknown”. See literals
- not
- Inverts the following boolean expression. Has a lower precedence than !
- or
- Boolean or with lower precedence than ||
- redo
- Restarts execution in the current block. See control expressions
- rescue
- Starts an exception section of code in a begin block. See exception handling
- retry
- Retries an exception block. See exception handling
- return
- Exits a method. See methods. If met in top-level scope, immediately stops interpretation of the current file.
- self
- The object the current method is attached to. See methods
- super
- Calls the current method in a superclass. See methods
- then
- Indicates the end of conditional blocks in control structures. See control expressions
- undef
- Prevents a class or module from responding to a method call. See modules and classes
- unless
- Used for unless and modifier unless statements. See control expressions
- until
- Creates a loop that executes until the condition is true. See control expressions
- when
- A condition in a case expression. See control expressions
- while
- Creates a loop that executes while the condition is true. See control expressions
- yield
- Starts execution of the block sent to the current method. See methods
总共 42 个词。也就是说，编写 Ruby 程序时，只需要也只能使用这些英文词。编程过程中，除了这些英文词以外，还会出现的英文词就是 Ruby 内置的方法了。
1 只是具有字面意义的变量。