Drain of Energy – weaken VS sap Vs enervate Vs enfeeble
Weaken is the most general word among these synonyms. It can refer to lessening of strength or power of anything.
Enervate and sap; both are used only for living beings.
Sap implies a gradual loss of strength.
Ex – Taking care of her entire family for years has sapped her strength.
Enervate focuses on loss of strength or weariness, as after an illness, due to working excessively etc.
Ex – He felt enervated after suffering from viral fever for a week.
Enfeeble also applies to people but it differs in indicating an extreme weakening.
Ex – The poor man was enfeebled by years of undernourishment.