A handshake is a globally widespread, brief greeting or parting tradition in which two people grasp one of each other's hands, and in most cases, it is accompanied by a brief up-and-down movement of the grasped hands. Customs surrounding handshakes are specific to cultures. Different cultures may be more or less likely to shake hands, or there may be different customs about how or when to shake hands.

Greeting is an act of communication in which human beings intentionally make their presence known to each other, to show attention to, and to suggest a type of relationship or social status between individuals or 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.