\ba Unicode word boundary
notthe literal text not (case sensitive) \s+a Unicode whitespace character, repeated at least once
checkthe literal text check (case sensitive) \ba Unicode word boundary
Negative Lookahead(?!\s*\d) \s*a Unicode whitespace character, repeated any number of times
\da Unicode decimal digit
\D*any character that is not a Unicode decimal digit, repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string