Let the center 
of a circle of radius 
move along a line 
.
Let 
be a fixed point located a distance
away from 
.
Draw a secant line through 
and 
, the midpoint
of the chord cut from the line 
(which is parallel to 
) and a distance 
away. Then the locus of the points
of intersection of 
and the circle 
and 
is called a kieroid.
| special case | curve |
 | conchoid of Nicomedes |
 | cissoid plus asymptote |
 | strophoid plus asymptote |
