Case sensitivity　　区分大小写

Case insensitive: Differences between uppercase and lowercase characters are ignored. cat matches CAT, Cat, or cAt or any other capitalization in addition to cat.
不区分大小写：忽略大小写字符之间的差异。cat匹配CAT, Cat,cAt或cat的其他任何大写字母.

Case sensitive: Differences between uppercase and lowercase characters are significant. cat matches only cat.
区分大小写：大小写字符之间的差异是显著的。cat只匹配cat。

Free-spacing mode　　自由间距模式

Free-spacing: Unescaped spaces and line breaks in the regex are ignored so you can use them to format your regex to make it more readable. In most applications this mode also makes # the start of a comment that runs until the end of the line.
自由间距：regex中未转义的空格和换行符被忽略，因此可以使用它们格式化正则表达式，使其更可读。在大多数应用程序中，此模式还使#成为注释的开头，直到行的结尾。

Exact spacing: Unescaped spaces, line breaks, and # characters in the regex are treated as literal characters that the regex must match.
精确间距：正则表达式中未转义的空格、换行符和#字符被视为正则表达式必须匹配的文字字符。

Single-line mode　　单线模式

Dot matches line breaks: The dot matches absolutely any character, whether it is a line break character or not. Sometimes this option is called “single line mode”.
点匹配换行符：点绝对匹配任何字符，无论它是否是换行符。有时此选项称为“单线模式”。

Dot doesn\’t match line breaks: The dot matches any character that is not a line break character. Which characters are line break characters depends on the application and the line break mode.
点不匹配换行符：点匹配任何不是换行符的字符。哪些字符是换行字符取决于应用程序和换行模式。

Multi-line mode　　多行模式

^$ match at line breaks: The ^ and $ anchors match after and before line breaks, or at the start and the end of each line in the subject string. Which characters are line break characters depends on the application and the line break mode. Sometimes this option is called “multi-line mode”.
^$匹配换行符:^和$锚匹配换行符的前后,或者匹配主题字符串中每一行的开始和结束。哪些字符是换行符取决于应用程序和换行模式。有时这个选项被称为“多行模式”。

^$ don\’t match at line breaks: The ^ and $ anchors only match at the start and the end of the whole subject string. Depending on the application, $ may still match before a line break at the very end of the string.
^$不匹配换行符：^和$锚只在整个主题字符串的开头和结尾匹配。根据应用程序的不同，$可能在字符串最末端的换行符之前仍然匹配。