Tick

A tick represents a 0.1 (1/10) second delay in the signal of a redstone circuit. That is, the signals time to travel from a location A to location B is increased by 0.1 (1/10) of a second. A tick only pertains to the increase in signal time, thus, a signals travel time can never be decreased in reference to ticks.

Methods to produce multiple or single ticks

 * 1) A single tick can be produced by placing down a block with a redstone torch on the side and input signal from the rear (opposite side to the torch).
 * 2) A tick can be produced by placing down a redstone repeater which, by default, has a tick of 1 when the two redstone torches are closest together. Right clicking the repeater will increase the tick by a level of 1 to 0.2 (2/10). A single redstone repeater can be configured to produce a tick of 4 (4-tick) on it's highest setting with the two redstone torches furthest apart.

Tick terminology
1-tick refers to a single tick in a circuit or other element of a circuit, such as a clock. Therefore, terms such as 8-tick should be interpreted as 8-tick delays (0.8 (8/10) of a second) and not as an 8 second delay.