Which word describes the action of reducing or lessening something by use or exhaustion?

The term that describes the action of reducing or lessening something by use or exhaustion is "deplete." This word is often used in contexts where resources, supplies, or energy are gradually diminished over time due to consumption or use. For instance, one could talk about depleting natural resources, such as water or minerals, through overuse. The essence of depletion conveys an ongoing process of reduction until a significant portion is exhausted.

In contrast, "deride" refers to mocking or ridiculing someone or something, which does not relate to reduction or exhaustion. "Decimate" implies destroying a large portion of something but originally referred to a specific form of punishment in Roman military contexts that involved killing one in every ten soldiers. While it implies destruction, it conveys a more substantial or violent action rather than a gradual lessening through use. "Decorum" pertains to proper behavior or etiquette, which is unrelated to the concept of reducing or lessening something. Thus, "deplete" is the most accurate choice for the described action.