Noun

• S: (n) deceleration, slowing, retardation (a decrease in rate of change) "the deceleration of the arms race"
• S: (n) retardation (the extent to which something is delayed or held back)
• S: (n) retardant, retardent, retardation (any agent that retards or delays or hinders) "flame-retardant"
• S: (n) retardation, mental retardation, backwardness, slowness, subnormality (lack of normal development of intellectual capacities)
• S: (n) slowdown, lag, retardation (the act of slowing down or falling behind)