energy
n. uncountablen. the physical and mental strength you need to do things. It also means the power from sources like electricity or the sun that makes machines work.
n. the physical or mental capacity for vigorous activity. In the physical sciences, it is the quantitative property transferred to a system to perform work or generate heat.
I do not have the energy to go for a run today.
The new solar panels generate enough renewable energy to power the entire office building throughout the year.
After weeks of intense negotiations, the diplomatic team lacked the emotional energy to celebrate their breakthrough, preferring instead to retreat to their hotel rooms for immediate rest.
From Middle French énergie, from Late Latin energia, from Ancient Greek ἐνέργεια (enérgeia, “activity”), from ἐνεργός (energós, “active”), from ἐν (en, “in”) + ἔργον (érgon, “work”). The sense in physics was coined by English polymath Thomas Young in 1802 in his lectures on Natural Philosophy.
Uncountable in both its general sense of vitality and its scientific sense of power; pluralised only in specific contexts like 'focusing one's energies'.