?Casually是一個副詞，意思是隨意地，不經意地，漫不經心地。它可以用來描述一種輕松的態度或者無拘束的表現。

用法：

Casually可以作為一個副詞，放在動詞之后，也可以放在句子的結尾。它可以修飾動詞，形容詞或者其他副詞。

例句1-5句且中英對照：

1. She was dressed casually for the party. 她穿著隨意參加聚會。

2. He casually mentioned that he was leaving town next week. 他隨口提到他下周要離開城市。

3. They were chatting casually over a cup of coffee. 他們邊喝咖啡邊隨意聊天。

4. The cat stretched out on the couch, looking very casual and relaxed. 貓舒服地躺在沙發上，看起來很隨意和放松。

5. She spoke casually about her upcoming trip to Europe. 她隨便談論她即將到歐洲旅行的事情。

同義詞及用法：

1. Informally - 非正式地，不拘束地。：They chatted informally over a cup of tea.

2. Nonchalantly - 漠不關心地，冷淡地。：He nonchalantly mentioned his resignation from the company.

3. Indifferently - 漠然地，冷漠地。：She shrugged her shoulders indifferently.

4. Laid-back - 悠閑的，輕松的。：He has a laid-back attitude towards life.

5. Unconcernedly - 漠不關心地，無動于衷地。：She walked away unconcernedly, not caring about the argument.