
click for a larger image
top: right circular cone
bottom: cones and rods of a human eye


1. Mathematics
a. The surface generated by a straight line, the generator, passing through a fixed point, the vertex, and moving along a fixed curve, the directrix.
b. A right circular cone.
a. The figure formed by a cone, bound or regarded as bound by its vertex and a plane section taken anywhere above or below the vertex.
b. Something having the shape of this figure: "the cone of illuminated drops spilling beneath a street lamp" (Anne Tyler).
3. Botany
a. A unisexual reproductive structure of most gymnospermous plants, such as conifers and cycads, typically consisting of a central axis around which there are scaly, overlapping, spirally arranged sporophylls that bear either pollen-containing structures or ovules.
b. A similar, spore-producing structure of club mosses, horsetails, and spikemosses.
c. A reproductive structure resembling a cone, such as the female inflorescence of a hop plant or the woody female catkin of an alder.
4. Physiology One of the photoreceptors in the retina of the eye that is responsible for daylight and color vision. These photoreceptors are most densely concentrated in the fovea centralis, creating the area of greatest visual acuity. Also called cone cell.
5. Any of various gastropod mollusks of the family Conidae of tropical and subtropical seas that have a conical, often vividly marked shell and that inject their prey with poisonous toxins, which can be fatal to humans. Also called cone shell.
tr.v. coned, con·ing, cones
To shape (something) like a cone or a segment of one.

[French cône and Middle English cone, angle of a quadrant, both from Latin cōnus, from Greek kōnos; see kō- in Indo-European roots.]


Receptor cells in the retina. They sense bright light and function in daylight. See retina.
References in classic literature ?
Certain tall white cones of rock rose out of the purple sea; they flushed in the afternoon light and their vague rosiness gave them a human expression in face of the cold expanse toward which the prow was turned; they seemed to say farewell, to be the last note of a peopled world.
Mother Atkinson put on her apron, turned up her sleeves, and fell to work as gaily as if in her own kitchen, boiling the kettle slung on three sticks, over a fire of cones and fir boughs; while the girls spread the mossy table with a feast of country goodies, and the children tumbled about in everyone's way till the toot of the horn made them settle down like a flock of hungry birds.