from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The curve traced out by points P and Pˌ which lie on lines through a fixed point A where the midpoint M of PPˌ is on a fixed line and the absolute value }PM} = the absolute value }PˌM} = the absolute value }MO}, where O is the projection of A onto that fixed line.
from The Century Dictionary and Cyclopedia
- n. A nodal plane cubic curve which is the locus of a focus of a conic whose directrix and two tangents are given.
- n. A curve which is the locus of intersections of two lines rotating uniformly with commensurable velocities. See also suhstrophoid.
Common decency and good taste prevents us from displaying Freeth’s supertrisectrix strophoid.
But Freeth’s nephroid is something altogether different: a strophoid of a circle with a double curlicue in the kidney crotch.