By default, every group is a capture group. A group can be marked as non-capturing using ?: before the expression. In the following example, the third group has been marked as a non-capturing group:

PS> 'first second third' -match '(?<One>first) (?<Two>second) (?:third)'; $matches

True

Name                             Value 
----                             ----- 
One                              first 
Two                              second 
0                                first second third 

The outer group that previously added second third to the matches list is now excluded from the results:

PS> 'first second third' -match '(first) (?:(second) (third))'; $matches
True

Name                                 Value 
----                                 ----- 
3                                    third 
2                                    second 
1                                    first 
0                                    first second third 

This technique may be useful when using replace; it simplifies the list of tokens available even if an expression grows in complexity:

PS> 'first second third' -replace '(first) (?:(second) (third))', '$1, $2, $3'
first, second, third