What term describes vibrations that gradually diminish as their source loses energy?

The term that describes vibrations that gradually diminish as their source loses energy is "damped." In a damped system, energy is dissipated over time due to factors like friction or resistance. As a result, the amplitude of the vibrations decreases until eventually coming to rest. This phenomenon is commonly observed in physical systems, such as a swinging pendulum that gradually stops due to air resistance and friction.

In contrast, amplified vibrations increase in amplitude, and resonant vibrations occur at particular frequencies that lead to significant increases in amplitude, often resulting in a dramatic effect. Reinforced vibrations also refer to an increase in strength due to constructive interference or additional energy input, rather than a gradual decrease. Thus, the term "damped" accurately reflects the behavior of vibrations losing energy over time, leading to a reduction in their amplitude.