An Etymological Dictionary of Astronomy and Astrophysics

The tendency of a → force applied to an object to cause the object to → rotate about a given → axis or → point. Torque is the rotational analogue of or the turning effect of a force. It is equal to the product of the force and its distance from the reference axis.

More specifically, if a force F acts on a single particle at a point P whose position with respect to the origin O of the inertial reference is given by the distance vector r, the torque T acting on the particle with respect to the origin O is defined as: T = r × F. Torque is a → vector quantity. Its magnitude is given by: rF sin θ, where θ is the angle between r and F; its direction is normal to the plane formed by r and F. The sense is given by the → right-hand screw rule for the → vector product of two vectors. Torque has the same dimensions as work, but work is a scalar.

Etymology (EN): From L. torquere “to twist;” cf. Skt. tarku- “spindle;” maybe Mod.Pers. duk “spindle;” Mid.Pers. dôk “spindle;” O.C.S. traku “band, girdle,” O.H.G. drahsil “turner,” Ger. drechseln “to turn on a lathe;” O.E. thweorh “transverse, perverse, angry, cross;” E. thwart; PIE base *twork-/*twerk- “twist”

Etymology (PE): Gaštâvar literally “that which makes turn, turning agent,” from gašt “turning,” past stem of gaštan, gardidan “to turn, to change” (Mid.Pers. vartitan; Av. varət- “to turn, revolve;” Skt. vrt- “to turn, roll,” vartate “it turns round, rolls;” L. vertere “to turn;” O.H.G. werden “to become;” PIE base *wer- “to turn, bend”) + âvar
agent noun of âvardan “to bring; to cause, produce” (Mid.Pers. âwurtan, âvaritan; Av. ābar- “to bring; to possess,” from prefix ā- + Av./O.Pers. bar- “to bear, carry,” bareθre “to bear (infinitive),” bareθri “a female that bears (children), a mother;” Mod.Pers. bordan “to carry;” Skt. bharati “he carries;” Gk. pherein; L. fero “to carry”).