In machining it is sometimes necessary to stop the motion of all axes for a given amount of time (for example to let the spindle come up to speed or wait for the coolant to start flowing). This is called dwell. It’s activated with the G04 command. The time is specified using a P-word and a number seconds (the number is a float so fractions of a second can be used).
For example: G04 P3.7
A common place to use the G04 dwell command is when starting a spindle of a machine. Because it can’t accelerate instantly to the desired speed we need to allow it some time to speed up before starting to cut the material. An example of code that waits 5 seconds after starting the spindle at 10000 RPM is here: