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) vector, transmitter (any agent (person or animal or microorganism) that carries and transmits a disease) "mosquitos are vectors of malaria and yellow fever"; "fleas are vectors of the plague"; "aphids are transmitters of plant diseases"; "when medical scientists talk about vectors they are usually talking about insects"
S: (n) vector ((genetics) a virus or other agent that is used to deliver DNA to a cell)