1. Delay; hindrance; delayed development.
2. The process or fact of slowing down.
3. Something that acts as a delay or obstacle to progress.
4. The extent to which something is held back or delayed.
5. Sometimes a reference to the lack of normal development of intellectual capabilities.

1. A sorbent extraction (taken up and held, as by absorption or adsorption or adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium) of strong electrolytes with an anion-exchange resin in which a cationic monomer has been polymerized, or the reverse.
2. A process based on bifunctional (two functional) ion-exchange resins containing both anion (negatively charged ion) and cation (positively charged ion) adsorption sites, which removes both kinds of ions from solutions.

Intellectual functioning that is significantly below average and is associated with impairment in social adjustment, manifested prior to maturity; usually early in life.

The term is specifically defined in different nations and by some professional organizations, but no single definition is accepted worldwide.

Delay in the attainment of motor skills, language development, and social responsiveness in infancy and childhood.

A marked discordance between the degree of motor retardation and that of social response and alertness, as revealed by testing, may predict either cerebral palsy or a primary intellectual impairment.

Mental retardation due to, or exaggerated by, cultural, social, and interpersonal inadequacies in the person's environment.