half-ray

Century Dictionary and Cyclopedia

1. n. In mathematics, the aggregate of all points of a straight which are on one and the same side of O, a point of the straight.

Wiktionary

1. n. geometry A ray, or half-line.

GNU Webster's 1913

1. n. (Geom.) A straight line considered as drawn from a center to an indefinite distance in one direction, the complete ray being the whole line drawn to an indefinite distance in both directions.