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 |
