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A clock face or instrument resembling a clock face.
[L. dies, day]
a circular diagram with black lines radiating outward across a white background from the center, as is used in tests of astigmatism.
dial(dī′ăl) [L. dialis, daily, fr. dies, day]
A graduated circular face, similar to a clock face, on which some measurement is indicated by a pointer that moves as the entity being measured (pressure, temperature, or heat) changes.
A circular dial with black lines of uniform width drawn as if they were connecting opposing numbers on the face of a clock. It is used in testing for astigmatism.