I'm writing documentation for a behavior of a device which has a button. When the user presses the button, the machine transitions from the state A into state B.
After the user releases the pressure on the button, that is to say, the button is no longer in the state of being pressed, the device will transition from state B into state C.
Since English uses "depress" to describe both the action of pressing the button, and the opposite action, I'm not sure how can I clearly and succinctly describe the action of releasing the pressure on the button.
Note: If possible, I'd prefer to use a single word, instead of a longer phrase.