- (initial segment of an ordered set) upphafsstúfur
= initial segment - (of a circle) sneið, hringsneið
= circular segment - (of a curve) bútur, bogi
- (of a line) strik, línustrik
= line segment - (spherical, of one base) sneið, kúlusneið, kúlukollur
= spherical segment 1, spherical segment of one base - (spherical, of two bases) kúluskífa
= spherical layer, spherical segment 2, spherical segment of two bases