The order of a dynamcial system or difference equation is the difference between the largest and the smallest arguments k appearing in it.
- y(k+1) = a(k)y(k)+b(k) has order 1
- y(k-3)-3y(k-4) = 0 has order 1
- y(k+3)+ay(k+1) = by(k-1) + c has order 4
- y(k+3) = 2/y(k-2) + (k-1) has order 5