S: (n) straight line (a line traced by a point traveling in a constant direction; a line of zero curvature) "the shortest distance between two points is a straight line"
S: (n) asymptote (a straight line that is the limiting value of a curve; can be considered as tangent at infinity) "the asymptote of the curve"
S: (n) tangent (a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point)
S: (n) secant (a straight line that intersects a curve at two or more points)
S: (n) radius (a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere))
S: (n) diameter (a straight line connecting the center of a circle with two points on its perimeter (or the center of a sphere with two points on its surface))
S: (n) chord (a straight line connecting two points on a curve)
S: (n) element (a straight line that generates a cylinder or cone)
S: (n) diagonal, bias (a line or cut across a fabric that is not at right angles to a side of the fabric)
S: (n) diagonal ((geometry) a straight line connecting any two vertices of a polygon that are not adjacent)
S: (n) vector (a straight line segment whose length is magnitude and whose orientation in space is direction)