# What is the difference between incremental and cumulative error?

In a description for ballscrews on a CNC, I saw two types of error listed:

• Incremental error: < 0.0006"/ft
• Cumulative error: < 0.0008" at 35"

What are these types of error measuring? What is the difference between them?

If the screw is commanded to move a distance $x$ (in any length unit!) the distance actually moved will be between 0.99995$x$ and 1.00005$x$ (because 0.0006/12 = 0.00005)