Order of magnitude:
An exponential change of plus or minus 1 in the value of a quantity or unit.

Example: 10E01 = 10, whereas 10E02 = 100; there is one order of magnitude difference between 10 and 100.

In Safety Integrity Level (SIL) terms, there is one order of magnitude difference between each SIL band of SIL 1, SIL 2, SIL 3 etc.