What is Backlash?

Backlash is pronounced "backlash", but in the case of technical terminology it is written as "backlash".
The term "Backlash" originated from gear engineering discipline. In JIS terminology, this word is described as: Play that exists between a pair of engaged gears' tooth surfaces. When described as a distance of an arc on the engagement pitch circle, it is called "Circumference Direction Backlash", when described as the shortest distance between two opposing tooth surfaces is called "Normal Line Backlash".

Causes of backlash in Ball Screws

Causes for ball screw backlash are:1) Axial clearance
2) Axial elastic deformation of nut
3) Elongation and contraction of screw shaft
4) Axial deformation due to tortional forces

The entire drive train mechanism must be taken in consideration when considering the subject of Backlash.

There is a method of backlash reduction caused by axial clearance and deformation of the contacting surfaces. It is called "Preloading" and is applied during ball screw assembly. This "Preload" is not to be confused with applied load on the system, but should be understood as internally built-in load.

By the way, how is "rush" different from rush hour (crowded time) or the rush (attack) in boxing? I looked it up in an English-Japanese dictionary as usual to find out why it is called backlash. Surprisingly, there are many different kinds of "rush."

lash：the tip of a whip, to attack violently, to tie up, to do something recklessly, to rock back and forth.
rash： reckless, short-tempered, hasty.
rush：to rush forward, to rush, torrential, busy, in a hurry.

Well, backlash doesn't quite fit, but it seems to mean something like "swaying backwards."
By the way, in German it's "Flanken spiel," which means "side play," and that's exactly what it means.
I found out that rush hour and rush (attack) are not really related. Also, for some reason, eyelashes are called eyelashes.