Answer by WolfmanDragon for What is a word boundary in regex?

A word boundary can occur in one of three positions:

1. Before the first character in the string, if the first character is a word character.
2. After the last character in the string, if the last character is a word character.
3. Between two characters in the string, where one is a word character and the other is not a word character.

Word characters are alpha-numeric; a minus sign is not.Taken from Regex Tutorial.