There are many collegiate secret societies in North America.
Most class societies are restricted to the senior class, and are therefore also called senior societies on many campuses.
There is no strict rule on the categorization of secret societies.
Secret societies can have ceremonial initiations, secret signs of recognition (gestures, handshakes, passwords), formal secrets, (the 'true' name of the society, a motto, or a society history); but, college fraternities or "social fraternities" have the same, and some of these elements can also be a part of literary societies, singing groups, editorial boards, and honorary and pre-professional groups.
Some secret societies have kept their membership secret, for example Seven Society and Gridiron, and some have not, like Skull and Bones (the Yale societies had published their membership lists in the yearbooks and the Yale Daily News).
There are additional means, such as societies that were more or less explicitly established in emulation of some previous secret society, or using historical records to show that society X was created out of society Y.