stamina

This term describes the internal reservoir of energy and willpower that allows a person to persist through exhaustion. It carries a connotation of grit and resilience, distinguishing itself from simple strength by emphasizing the duration of the effort rather than the intensity of a single burst. As an uncountable noun, stamina cannot be pluralized or counted with numbers. To quantify it, one must use partitive phrases such as a great deal of stamina or a lack of stamina.