A number of terms are used to help describe the movement of the major joints of the body. The terms can be used with precision although, because movement is occurring in a three-dimensional space, precise use requires identification of dimensional axes and planes. More commonly the terms are used with greater regard to practical meaning than anatomical theory and a selection of terms can provide a reasonable description of most movements. Terms are usually paired to distinguish movement in one direction from the reverse. Flexion is a movement that decreases the angle between the body part and the adjacent segment (e.g. the upper and lower arm). Extension is the reverse movement. Hyper-extension, extending the limb beyond its normal range, is possible at some joints and well illustrated in gymnasts and swimmers. Abduction is the movement of a body part upward and away from the midline (e.g. the arm at the shoulder). Adduction is the reverse. Plantar flexion refers to the ankle joint and is the movement of pointing the toes down. Dorsiflexion is the opposite. Inversion refers to turning the soles of the foot inwards so the soles point towards each other. Eversion is the opposite. Rotation is the twisting of a bone around its own long axis and this may be medial rotation (inwards, towards the midline) or lateral rotation (outwards, away from the midline). Elevation refers to the movement of a body part upwards and depression the reverse, such as the shrugging of the shoulders. Circumduction is a movement that combines flexion–extension–abduction–adduction so the end of a limb or bone moves in a circle.