- A tree of the genus Ulmus, of several species, much used as a
shade tree, particularly in America. The English elm is Ulmus
campestris; the common American or white elm is U. Americana; the
slippery or red elm, U. fulva.
Young-Helmholtz Theory Young-Helmholtz Theory is the best known theory of colour vision which suggests that the retina contains three types of colour receptors for red, green and blue and that all other
Definition
[ n.]