ELBOW

elbow, in anatomy, the articulation of the _humerus_, the bone of the upper arm, and the _ulna_ and _radius_, the bones of the forearm (see joints). the word is thus applied to things which are like this joint in shape, such as a sharp bend of a stream or river, an angle in a tube, &c. the word is derived from the o. eng. _elnboga_, a combination of _eln_, the forearm, and _boga_, a bow or bend. this combination is common to many teutonic languages, cf. ger. _ellbogen_. _eln_ still survives in the name of a linear measure, the "ell," and is derived from the o. teut. _alina_, cognate with lat. _ulna_ and gr. [greek: olene], the forearm. the use of the arm as a measure of length is illustrated by the uses of _ulna_, in latin, cubit, and fathom.