substitution (sub-sti-tu's hun). 1

In chemistry, the proce of replacing one or more atoms in a molecule by other atoms or radicles. 2. In physiology and pathology, compensatory or vicarious action; a manifestation of disease in alternation with another and especially a nervous disorder; of French writers, replacement of the ti ue of an organ by an inflammatory product. 3. In pharmacy; the sale of a substitute for an article prescribed or asked for. 4. In psycho-analysis the carrying over of an emotional conflict to an indifferent idea. s. product. In chemistry, a product of the reaction of two bodies in which a molecule of the one replaces a portion of the molecule of the other. [Lat., substituere, to substitute.]