trembling

This term captures a specific type of vibration that is rapid, small, and involuntary. It is heavily associated with internal emotional states, such as terror or anticipation, or physiological responses to extreme cold. While shaking can be violent or intentional, trembling suggests a fragility or a loss of control over one's own muscles.

As a noun, the word functions as a gerund describing the state of vibration. It is typically treated as an uncountable mass noun when referring to the general phenomenon of shaking, though it can occasionally be used in a countable sense when referring to specific instances or episodes of the action.