What is the mathematical term for 'stepping' by a given value. In the many early learner books for young children, things like addition and subtraction are explained as stepping a particular amount. For example, in this number line: > 1, 3, 5, 7, ... It is explained that we are 'stepping' up and down by 2. Is there a mathematical term for the amount we move rather than stepping, or to put another way, a more generic mathematical term that covers both "increment by" and "decrement by"?

This is called an _arithmetic progression_ or _arithmetic sequence_ and the amount that you add at each step is called the _common difference_ of the progression, because consecutive terms of the progression all have the same difference.