enervate
To drain someone’s energy and make them feel very weak.
To enervate means to drain someone's energy or strength, leaving them feeling weak and tired. When heat and humidity enervate you during a summer afternoon, you feel exhausted and can barely move. A long, boring lecture might enervate students, sapping their attention and making them slump in their seats.
Unlike simple tiredness from physical work, enervation often comes from draining circumstances: oppressive heat, tedious tasks, or discouraging situations that wear you down mentally and physically.
Be careful not to confuse enervate with “energize,” even though they sound similar. They're actually opposites. While a brisk morning run might energize you, spending three hours stuck in a stuffy waiting room would enervate you. Similarly, don't mix up enervate with “unnerve,” which means to make someone nervous or afraid rather than tired. An enervating experience leaves you exhausted, while an unnerving one leaves you anxious.
When you feel enervated, you need rest and renewal, not just a quick break. It's that bone-deep weariness that takes real recovery time.