[Regex]::Matches($string, '(?:^|\b)words(?:$|\b)')Matches only the specific word in the express. In this case words will return, but passwords will not.
PS C:\> $string = 'A passwords should not contain words found in the dictionary.'
>> [Regex]::Matches($string, '(?:^|\b)words(?:$|\b)')
Groups : {0}
Success : True
Name : 0
Captures : {0}
Index : 31
Length : 5
Value : words