The following keywords are reserved and cannot be used as identifiers:

Lua is a case-sensitive language: is a reserved word, but And and AND are two different, valid identifiers. As a convention, identifiers starting with an underscore followed by uppercase letters (such as _VERSION) are reserved for internal variables used by Lua.

Literal strings can be delimited by matching single or double quotes, and can contain the following C-like escape sequences:

• \a —- bell
• \b —- backspace
• \f —- form feed
• \r —- carriage return
• \t —- horizontal tab
• \v —- vertical tab
• \" —- quotation mark
• \' —- apostrophe
• \[ —- left square bracket

Moreover, a `\newline´ (that is, a backslash followed by a real newline) results in a newline in the string. A character in a string may also be specified by its numerical value using the escape sequence `\ddd´, where ddd is a sequence of up to three decimal digits. Strings in Lua may contain any 8-bit value, including embedded zeros, which can be specified as `\0´.

Numerical constants may be written with an optional decimal part and an optional decimal exponent. Examples of valid numerical constants are

Comments start anywhere outside a string with a double hyphen (--). If the text immediately after -- is different from [[, the comment is a short comment, which runs until the end of the line. Otherwise, it is a long comment, which runs until the corresponding ]]. Long comments may run for several lines and may contain nested [[ · · · ]] pairs.