Stereotactic is derived from the Greek words stereos, meaning solid (as in 3-dimensional) and taxis, meaning arrangement, order, or orientation. Stereotactic radiation therapy (SRT) implies the use of technologies, which improve targeting accuracy and allow for hypofractionated radiation delivery. Generally, a 3-dimensional coordinate system is used to localize the target(s) most accurately. Stereotactic techniques can be used with conventional fractionation (1.8–2 Gy per day), but because of improved targeting accuracy, SRT allows for hypofractionated radiation (larger doses per fraction, fewer number of fractions, and a shorter treatment course). Also called stereotactic external-beam radiation therapy and stereotaxic radiation therapy.