retinal

adj : in or relating to the retina of the eye; "retinal cells"

n : either of two yellow to red retinal pigments formed from

Rhodopsin by the action of light [syn: {retinene}]

rational

[Mathematics] a fractional number n/d, where n and d are

integers, n is the numerator and d is the denominator. The

set of all rational numbers is usually called Q.

Computers do not usually deal with rational numbers but

instead convert them to {real} numbers which are represented

(approximately in some cases) as {floating-point} numbers.

Compare {irrational}.