in geometry, a line that cuts another or divides it into parts. The secant of a circle is a line drawn from the circumference on one side to a point without the circumference on the other; and it is demonstrated by geometers, that of several secants drawn to the same point, that is the longest which passes thro' the centre of the circle. The portions, however, of these several secants that are without the circle are so much the greater as they recede from the centre, and the least external portion is of that secant which passes through it.

in trigonometry, denotes a right line drawn from the centre of a circle, which, cutting the circumference, proceeds till it meets with a tangent to the same circle. See GEOMETRY, no. 24—28.

Line of SECANTS, one of those lines or scales which are usually put upon sectors. How such a scale is formed will be seen by a bare inspection of fig. 53. Plate CCXV.; for C 10, C 20, C 30, &c., drawn from the centre C to the line of tangents BE, being the real secants of the arches B 10, B 20, B 30, it is obvious that by marking off the distances B 10, B 20, B 30, upon any other line, we make that line a scale of secants.