equanimity
Word family adjectiveequanimousnounequanimityadverbequanimously
eq·ua·nim·i·ty /ˌiːkwəˈnɪməti, ˌekwə-/ noun [uncountableU] formalCALM calmness in the way that you react to things, which means that you do not become upset or annoyed 〔对某事反应的〕平和,镇静,沉着 He received the news with surprising equanimity. 他得到消息时显得异常镇静。
Origin equanimity (1600-1700) Latin aequanimitas, from aequo animo “with level mind”