The "domino effect" is the idea that some change, small in itself, will cause a similar change nearby, which then will cause another similar change, and so on in linear sequence, by analogy to a falling row of
dominoes standing on end. A well-known use of this metaphor was a justification for the
Vietnam War: if
Vietnam fell to
communism, then
Cambodia would be next, then
Laos, and eventually all of Southeast Asia.
See also:
Butterfly effect,
Snowball effect,
Mathematical induction