tax·is 
(tăksĭs)
(tăksĭs)n. pl. tax·es (tăksēz)
1. Biology The responsive movement of a free-moving organism or cell toward or away from an external stimulus, such as light.
2. Medicine The moving of a body part by manipulation into normal position, as after a dislocation, fracture, or hernia.
[Greek, arrangement, from tassein, tag-, to arrange.]