A correction is a relatively small (compared to a crash) downward movement in a market. It is usually an interruption of an upward trend that has risen: the market rises too fast, this is corrected by a fall, and the market can then return to normality.
Unlike a crash, a correction has no lasting effect on sentiment and does not lead to a prolonged period of weak performance.
The term correction is sometimes used by commentators who wish to talk down the importance of a downward movement, and therefore avoid terms such as “fall”.