insouciance

n [U] (fml 文) state of being unconcerned, esp in a light-hearted way; nonchalance 无忧无虑; 满不在乎; 漠不关心; 漫不经心.

insipidity, insipidly, insist, insist on sth. (doing sth.), insist upon, insistence, insistent, insistently, insofar, insofar as, insole, insolence, insolent, insolently, insoluble, insolvency, insolvent, insomnia, insomniac, insomuch, insouciant, Insp, inspect, inspection, inspector, inspector of taxes (also tax inspector), inspectorate, inspiration, inspirational, inspire, inspired, inspiring, Inst, instability, instable, install, install (US also instal), installation, installment, instalment,