semimajor axis

English Thesaurus

1. one-half the major axis of an ellipse; the distance from the center of an ellipse to one end (noun.cognition)

hypernym	:	axis,
definition	:	a straight line through a body or figure that satisfies certain conditions (noun.cognition)

part meronym	:	major axis,
definition	:	the longest axis of an ellipse or ellipsoid; passes through the two foci (noun.cognition)