Regular Expressions 101

Negative Lookbehind(?<!isn't )

isn't the literal text isn't (case sensitive)

Negative Lookbehind(?<!not )

not the literal text not (case sensitive)

\ba Unicode word boundary

Non-Capturing Group(?:good|great)

1st Alternativegood

goodthe literal text good (case sensitive)

2nd Alternativegreat

greatthe literal text great (case sensitive)

\ba Unicode word boundary

Global pattern flags

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

(?<!isn't )(?<!not )\b(?:good|great)\b

New

good words
not good words
isn't good words
great words
not great words
isn't great words
words good
words not good
words isn't good
words great
words not great
words isn't great
words good words
words not good words
words isn't good words
words great words
words not great words
words isn't great words

Regular Expression

Substitution