问候是一种人与人（以及动物与动物）或群与群之间表达互相知晓、关心或者显示一种关系（通常密切）或是社会地位的交流方式。问候有时只是在开始对话或在路过时，例如在人行道上。不同文化中的问候方式不同，同一文化中不同社会地位和社会关系的人之间的问候方式也不尽相同，但是，所有已知的人类文化都存在着问候的风俗。人与人见面时的问候可以带有声音，也可以通过肢体的行为来表示，往往涉及两者的结合。本话题不包括军事和仪式上的敬礼，不过包括手势意外的其他仪式。沟通也可以以书面交流的方式表达，例如书信和电子邮件。

有些世代和文化有非常复杂的问候仪式，例如问候君主。相反地，秘密结社通常有暗号或晦涩难懂的问候形式，比如秘密握手，允许成员彼此识别。

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 (usually cordial) or social status (formal or informal) between individuals or groups of people coming in contact with each other. Greetings sometimes are 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.