PRIMUS, an appellation given to whatever is first in order, degree, or dignity, among several things of the same or like kind; thus we say, the prime minister, prime cost, &c.

Prime is sometimes used to denote the same with decimal, or the tenth part of an unit.

PRIME Figure, in Geometry, one which cannot be divided into any other figures more simple than itself, as a triangle among planes, and the pyramid among solids.

For prime numbers, in arithmetic, see the article NUMBER.

PRIME of the Moon, is the new moon when the first appears, which is about three days after the change.

PRIME Vertical, is that vertical circle which passes through the poles of the meridian, or the east and west points of the horizon; whence dials projected on the plane of this circle are called prime vertical, or north-and-south dials.

in the Romish church, is the first of the canonical hours, succeeding to lauds.

in Fencing, is the first of the chief guards. See GUARD.