casually

He casually mentioned that he had won the lottery while eating lunch with his friends.

(Chinese) 和朋友吃午饭时，他漫不经心地提到自己中了彩票。

She dressed casually in jeans and a t-shirt for the outdoor garden party.

(Chinese) 她穿着牛仔裤和T恤，很随意地参加了户外花园派对。