is a specific kind of: line.

is a broader term that covers: bell-shaped curve, Gaussian curve, Gaussian shape, normal curve | meander | closed curve | S-shape | catenary | Cupid's bow | undulation, wave | extrados | gooseneck | intrados | bend, crook, turn, twist | crotchet, hook | envelope | arc | crenation, crenature, crenel, crenelle, scallop | spiral | helix, spiral | perversion | sinuosity, sinuousness | arch | bell, bell shape, campana | arc, bow | crescent | quadric, quadric surface | lemniscate | line roulette, roulette ... show more.

is the opposite of: straight line.

derivation: curve, cut, sheer, slew, slue, swerve, trend, veer.