U′ni‐ax″i‐al (?), a. [Uni + axial.] 1. (Crystallog.) Having but one optic axis, or line of no double refraction.
☞ In uniaxial crystals, the optic axis has the direction of the vertical crystallographic axis. All tetragonal and hexagonal crystals are uniaxial.
2. (Biol.) Having only one axis; developing along a single line or plane; — opposed to multiaxial.