Postural: Pertaining to the posture or position of the body, the attitude or carriage of the body as a whole, or the position of the limbs (the arms and legs). Postural hypotension is a drop in blood pressure (hypotension) due to a change in body position (a change in posture). It occurs when a person, often an older person, moves to a more vertical position: from sitting to standing or from lying down to sitting or standing. The change in posture causes a temporary reduction in blood flow and therefore a shortage of oxygen to the brain, which leads to lightheadedness and, sometimes, a "black out" episode, a loss of consciousness.
The root of the word "posture" is the Latin verb "ponere" meaning "to put or place." The past participle "positus" gave the noun "positura" that travelled via France to England in the 16th century as "posture."