TipA regular expression is a pattern describing a certain amount of text. Their name comes from the mathematical theory on which they are based. There are many Internet sites that instructions, examples or tutorials for regular expressions.
Accordingly, Regular Expressions are beyond the scope of these used Helps.
TipYou can use regular expressions when you work with filters or use Find.
https://msdn.microsoft.com/en-us/library/az24scfc%28v=vs.110%29.aspx has tables of various operators. Phonology Assistant uses this system.
http://www.regular-expressions.info/tutorial.html has a tutorial.
You may want to save regular expressions that work well for you in a document that you edit in a Unicode-compliant text editor.