retard
UK: rɪˈtɑːd | US: rɪˈtɑːrd
vt. to delay or slow the progress of something
n. (offensive) a person with limited intellectual development (dated/pejorative usage)
The word "retard" originates from Latin retardare ("to make slow"), combining re- (back) and tardus (slow). Initially neutral, it entered English in the 15th century as a verb meaning "to delay." By the 18th century, it gained a noun form to describe developmental delays, which later became a pejorative term. Modern usage avoids the noun form due to its offensive connotations, though the verb remains in technical contexts (e.g., "flame retardant").
The chemical additive helps retard the spread of fire.
Heavy traffic may retard your arrival time.
(Avoid noun usage due to offensiveness.)
Cold weather can retard plant growth.
Engineers designed materials to retard corrosion.