Friendship among women: A woman doesn't come home at night. The next day she tells her husband she slept over at a friend's house. The man calls
his wife's ten best friends. None of them know about it.

Friendship among men: A man doesn't come home at night. The next day he
tells his wife he slept over at a friend's house. The woman calls her
husband's ten best friends. Eight of them say he slept over. Two claim
he's still there.