Mouse acceleration makes your mouse move faster as you move it in a direction, this can make certain tasks difficult and some users just prefer linear movement. Here's the instructions on how to disable it:
1. Press command + space to open spotlight search, type "terminal" and press enter
2. Enter the following command into the terminal:
"defaults write .GlobalPreferences com.apple.mouse.scaling -1"
This will disable mouse acceleration. If you want to check and see if what the current setting is, enter the following command into the terminal:
"defaults read .GlobalPreferences com.apple.mouse.scaling"
This will return a value, if you used the previous command to disable acceleration, the returned value should be "-1".
You can also use the first command to turn acceleration back on by using the value "1" rather than "-1".
Note: This article only applies to an Apple Mac Mouse. If you use a 3rd party mouse such as a Logitech or SteelSeries, you will most likely need to install the software that came with your mouse in order to disable acceleration.