Which word describes self-confident assurance?

The term that best describes self-confident assurance is "aplomb." This word captures the essence of being poised, composed, and self-assured in situations that may come with pressure or complexity. Aplomb suggests a strong, steady presence that conveys confidence without crossing into negative connotations. It embodies an elegant confidence that allows individuals to navigate challenges gracefully.

In contrast, while "confidence" also denotes a sense of self-assurance, it lacks the nuance of composure and steadiness that aplomb conveys. Arrogance and hubris, on the other hand, carry negative implications; they refer to an inflated sense of self that overwhelms humility, rather than a balanced and composed form of assurance. Thus, aplomb is the most fitting term for describing self-confident assurance.