Definition. A tick is a contract's minimum price increment. The tick value is the amount by which one contract's value changes on a one-tick move.
How it works
For MYM the minimum increment is 1 index point, worth $0.50 per contract. For the full-size YM contract it's $5.
Example
A 40-tick move on MYM changes the value of one contract by $20.
What to watch out for
Don't confuse the tick as a price unit with the TICK indicator, which measures the behaviour of the whole stock market.
This is the Renko with NYSE TICK and ADD in the Hetman Terminal (Trend Formation). Screenshot from the Hetman Index (IHA) – a training instrument, simulated data. See all the Hetman Terminal tools →
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You'll find the full explanation with graphics, examples and exercises in the 📖 Order flow encyclopedia space, and its use in the live market in the 🔴 Live Room. Both are available to Club members (in Polish).