An expression is a combination of fields, values, operators, and functions that yields a result upon evaluation. Expressions can be used when filtering throughout the Tabs3 Software, and in several areas of PracticeMaster. An expression is considered a Query expression or Boolean expression if it is evaluated as true or false. A regular expression returns a string or a number upon evaluation. Regular expressions include Boolean expressions because Boolean expressions can be considered numerical since false is equivalent to 0 and true is equivalent to 1.