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[Gr. kōnos, pine cone]

1. A solid or hollow three-dimensional figure with a circular base and sides sloping up to a point.
2. In the outer layer of the retina, any of the flask-shaped cells that are stimulated by the wavelengths of light of different colors. The cones are essential for color discrimination.
SYN: SEE: retinal cone; SEE: cone cell
SEE: retina for illus.; SEE: rod; SEE: rod cell
3. A hollow, tapered, cylindrical device used in upper-extremity exercise to improve grasp, coordination, and range of motion.
4. A device on a dental radiography machine that indicates the direction of the central beam and helps to establish the desired source-to-film distance.

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