Step size ($h$)
The distance between consecutive points of the discretization.
Definition
The step controls the resolution of a mesh or of an ODE integration. Truncation error is written as powers of , and computational cost grows as it shrinks: choosing is a trade-off between accuracy, cost and stability.
How it is used
In stiff problems stability rules rather than accuracy: the admissible step can be far smaller than the truncation error suggests.