kathis-, cathis-, kathiso-, cathiso- +

(Greek: to sit; sitting)

acathistus
Not sitting.

The title of a certain hymn; or, better, an office in the Greek Liturgy, in honor of the Mother of God.

The title is one of eminence; since, while in other similar hymns the people are permitted to sit during part of the time, this hymn is partly read, partly sung, all standing (or, perhaps, standing all night).

akathisia
1. Uncontrollable limb and body movements, usually caused by drugs, especially some antipsychotic drugs.
2. A movement disorder characterized by a feeling of inner restlessness and a compelling need to be in constant motion as well as by actions; such as, rocking while standing or sitting, lifting the feet as if marching on the spot and crossing and uncrossing the legs while sitting.

People with akathisia are unable to sit or keep still, complain of restlessness, fidget, rock from foot to foot, and pace back and forth.

Akathisia is often a side effect of certain drugs.

kathisomania
An uncontrollable compulsion to sit down.
kathisophobia, cathisophobia (s) (noun); kathisophobias, cathisophobias (pl)
1. An excessive or abnormal avoidance of taking a seat: When someone has kathisophobia or cathisophobia, he or she may actually have anxieties about being trapped or is unable to sit still.

A kathisophobia may become the source of fear because it can be painful or uncomfortable in some people, especially the elderly who may be forced to be seated for longer times than younger persons, simply because they are not as ambulatory or capable of walking.

2. Etymology: from Greek kathizein, "to sit down" + phobia, "strong" or "irrational fear".