r groups of people coming in contact with each other. Greetings are sometimes used just prior to a conversation or to greet in passing, such as on a sidewalk or trail. While greeting customs are highly culture- and situation-specific and may change within a culture depending on social status and relationship, they exist in all known human cultures. Greetings can be expressed both audibly and physically, and often involve a combination of the two. This topic excludes military and ceremonial salutes but includes rituals other than gestures. A greeting, or salutation, can also be expressed in written communications, such as letters and emails. Some epochs and cultures have had very elaborate greeting rituals, e.g. greeting a sovereign. Conversely, secret societies have often furtive or arcane greeting gestures and rituals, such as a secret handshake, which allow members to recognize each other.