A theory of mathematical structure in which smooth continuous inputs lead to discontinuous responses. Water suddenly boils, ice melts, a building crashes to the ground, or the earth unexpectedly buckles and quakes. The French mathematician René Thom conceived and developed an eclectic collection of ideas into catastrophe theory. His idea was to establish a new basis for a more mathematical approach to biology. Connotations of disaster are misleading, since Thom's intention was to emphasize sudden, abrupt changes.