nonchalance

一副若无其事的样子

an appearance or manner of being calm and unconcerned

一种冷静、不关心的外表或态度

若无其事地

done in a calm and casual way, without showing much interest or anxiety

以一种冷静、随意的态度完成，不表现出太多兴趣或焦虑

假装若无其事

to pretend to be calm and unconcerned, especially when you are actually worried or interested

伪装冷静和不关心，尤其是在你实际担心或感兴趣的时候

装作若无其事

to pretend to have an appearance of being calm and unconcerned, often in a slightly artificial way

伪装出一种冷静、不关心的样子，通常带点不自然