nodding your head no is an example of
a gesture
title: Nod (gesture) text: Nod (gesture) A nod of the head is a gesture in which the head is tilted in alternating up and down arcs along the sagittal plane. In many cultures, it is most commonly, but not universally, used to indicate agreement, acceptance, or acknowledgement. Different cultures assign different meanings to the gesture. Nodding to indicate "yes" is widespread, and appears in a large number of diverse cultural and linguistic groups. Areas in which nodding generally takes this meaning include the Indian subcontinent (note that the head bobble also shows agreement there), the Middle East, Southeast Asia, most of Europe (see below), title: Nod (gesture) text: some countries swapping the meanings between nodding and shaking head: in Greece, Iran, Lebanon, Syria, Turkey, Egypt, Bulgaria, Albania, and Sicily a single nod of the head up (not down) indicates a "no". Specifically in Greece, the single nod of the head up that indicates "no" is almost always combined with a simultaneous raise of the eyebrows and most commonly also with a slight (or complete) rolling up of the eyes. There is also a sound that sometimes accompanies the whole gesture, called "τσου". This sound bears heavy resemblance, but is not identical, to the British tutting sound. The use title: Nod (gesture) text: of "τσου" is optional and reserved only for heavy emphasis on the "no". The emphasis on the raised eyebrows and the rolling up of the eyes is such, that the actual nod of the head upwards has ended up being of secondary importance. A person can denote "no" by simply raising their eyebrows and rolling up their eyes, with the head staying completely still. Nodding can also be used as a form of nonverbal greeting or acknowledgement of another's presence; in this context, it is essentially an especially mild form of bowing, with just enough movement to show a degree title: Head shake text: the Indian subcontinent, the Middle East, Africa, Southeast Asia, Europe (Greece included), South America, North America and Australia. However, in some Southeastern European areas such as Bulgaria and southern Albania, it is used for the opposite purpose, to indicate affirmation, meaning "yes". In those regions, nodding in fact means "no" as well, the complete reverse of most other places in the world. There are varying theories as to why head shake is so frequently used to mean "no". One simple theory is that it is most common form of expressing negative reaction, indicating that one disagrees with the other person. title: Cervical vertebrae text: to pass in front of the transverse process, and not through the foramen. The movement of nodding the head takes place predominantly through flexion and extension at the atlanto-occipital joint between the atlas and the occipital bone. However, the cervical spine is comparatively mobile, and some component of this movement is due to flexion and extension of the vertebral column itself. This movement between the atlas and occipital bone is often referred to as the "yes joint", owing to its nature of being able to move the head in an up-and-down fashion. The movement of shaking or rotating the head