groups command

[linuxboy]

Hi
when I use command groups it shows discrepancy with /etc/groups
#groups vivian
vivian : dba admin

#grep vivian /etc/group
admin:x:2201:vivian
#grep dba /etc/group
dba:x:2015:

dba a is a group local to system, Could someone explain why this is showing like this

[dalek]

I don't know why it is doing that but I get similar results here.  I'm listed in a lot of groups in /etc/groups but the groups command only shows a few of them.  Perhaps they are not "active" or something??  It's interesting.