He spoke with a natural ease that put everyone at ease.

ease 是名词，意思是"轻松、自在、不费力"的状态。这个词也可以作动词表示"缓解、减轻"。 put someone at ease 是一个固定短语，意思是"使某人放松、让某人感到自在"。这里的 at ease 表示"放松、舒适"的状态。