“镇静的”常见英文表达有 calm、composed、serene 等，具体使用哪个词取决于语境：
calm：最常用，形容人或环境平静、不激动，无焦虑或紧张。例句：He remained calm under pressure.（他在压力下保持冷静。）
composed：侧重于自制力，指在紧张或混乱中保持镇定。例句：She was very composed during the interview.（她在面试中表现得非常镇定。）
serene：更强调内心的平静与安宁，带有优雅或超脱的意味。例句：He had a serene expression on his face.（他脸上露出平静的表情。）