Circle

(sĭr'kl, 18), n. [A.-S. circol, circul, Fr. & Pr. cercle, It. circolo, Sp. & Pg. circulo, from Lat. circulus, dim. of circus, circle, Gr. κίρκος, circle, ring.]

1. A plane figure, bounded by a single curve line called its circumference, every part of which is equally distant from a point within it called the center.
2. The line that bounds such a figure; a circumference; a ring.
3. (Astron.) An instrument of observation, the graduated limb of which consists of an entire circle.

When it is fixed to a wall in an observatory, it is called a mural circle; when mounted with a telescope on an axis and in Y’s, in the plane of the meridian, it is called a meridian or transit circle; when involving the principle of reflection, like the sextant, it is called a reflecting circle; and when that of repeating an angle several times continuously along the limb, a repeating circle. 4. A round body; a sphere; an orb. It is he that sitteth upon the circle of the earth. Is. xi. 22.

5. Compass; circuit. “In the circle of the forest.” Shak.
6. A company assembled, or conceived to assemble, about a central point of interest, or bound by a common tie; a coterie; a set.

As his name gradually became known, the circle of his acquaintance widened. Macaulay. 7. A series ending where it begins. Thus in a circle runs the peasant’s pain. Dryden.

8. (Logic.) A form of argument in which two or more unproved statements are used to prove each other; inconclusive reasoning.
9. Indirect form of words; circumlocution.

Has he given the lie, In circle, or oblique, or semicircle. Fletcher. 10. A territorial division; a province or principality. “The several circles of the empire.” Temple. Circle of altitude, or almucantar (Astron.), a circle parallel to the horizon, having its pole in the zenith.—Circle of latitude, (a.) (Astron.) A great circle perpendicular to the plane of the ecliptic, passing through its poles. (b.) (Spherical Projection.) A small circle of the sphere whose plane is perpendicular to the axis.—Circles of longitude, lesser circles parallel to the ecliptic, diminishing as they recede from it.—Circle of perpetual apparition, at any given place, the boundary of that space around the elevated pole, within which the stars never set. Its distance from the pole is equal to the latitude of the place.—Circle of perpetual occultation, at any given place, the boundary of that space around the depressed pole, within which the stars never rise.—Circle of the sphere, a circle upon the surface of the sphere, called a great circle when its plane passes through the center of the sphere; in all other cases, a small circle.—Diurnal circles, immovable circles supposed to be described by the several stars and other points in the heavens in their apparent diurnal rotation round the earth.—Druidical circles (Eng. Antiq.), certain ancient inclosures formed by rude stones circularly arranged; as Stonehenge, near Salisbury.—Horary circles (Dialing), the lines on dials which show the hours. Syn.—Ring; circlet; compass; circuit; orb; inclosure; assembly.