-ärˌkizəm noun
( -s )
Usage: usually capitalized
Etymology: J. B. de Monet Lamarck, its formulator + English -ism
: a theory of organic evolution asserting that environmental changes cause structural changes in animals and plants especially by inducing new or increased use of organs or parts resulting in adaptive modification or greater development and similarly cause disuse and eventual atrophy of other parts and that such changes are transmitted to offspring — compare darwinism , evolution 5 b, neo-lamarckism