A tick in financial markets measures the smallest possible price fluctuation for any given asset. One tick is worth a certain amount of money, which varies depending on the asset being traded (the tick size or tick value).
A tick is the smallest incremental amount at which a security can be traded. Since 2001, when decimalization was implemented, the minimum tick size for stocks trading above $1 has been one cent.

A tick is a measure of the minimum upward or downward movement in the price of a security. A tick can also refer to the change in the price of a security from one trade to the next trade.