(optics) A doubly refracting crystal in which the index of refraction for the extraordinary ray is greater than for the ordinary ray, and the former is refracted nearer to the axis than the latter, such as quartz and ice; as opposed to negative crystal: one in which this characteristic is reversed, such as Iceland spar or tourmaline.

(grammar) That state of an adjective or adverb indicating simple quality, without comparison or relation to increase or diminution; as in wise, noble.

(medicine, bacteriology, of a bacterium) That is stained violet by Gram's method

A result of a test that shows as present something that is absent. / (statistics) type I error

(biology) referring to an RNA strand that can serve directly as messenger RNA and be transcribed into DNA.

(advertising) One of four archetypal dramatic structures of commercials, characterized by an emotionally neutral beginning with an enormous leap in positive emotions generated by seeing the branded product in use.

Infected by HIV.

(law) Law explicitly made, as compared to natural law, prescribed by express enactment or institution.

plural of positive law

plural of pole position