?down bad是一種俚語，通常用來形容某人處于情感低谷或者處境艱難的狀態。它可以用作形容詞或者副詞，表示某人的心情不好或者遇到了困難。

用法：

down bad通常用來描述某人的情緒或者狀況，表示他們感覺不好或者處于困境中。它可以單獨使用，也可以和其他詞組合在一起使用，down bad day（糟糕的一天）、feeling down bad（心情很差）等。

例句1-5句且中英對照：

1. She's been going through a lot lately, she's really down bad.（她最近經歷了很多事情，她真的很down bad。）

2. After losing his job and breaking up with his girlfriend, he's been feeling down bad for weeks.（失業和分手后，他已經有幾個星期感覺很down bad了。）

3. I had a really down bad day at work today, nothing seemed to go right.（我今天工作真的很down bad，什么都不順利。）

4. My friend has been down bad since her pet passed away.（我的朋友從她的寵物去世后就一直down bad。）

5. He's always there for me when I'm feeling down bad, I'm so lucky to have him as a friend.（當我感覺down bad時，他總是在我身邊，我很幸運有他這樣的朋友。）

同義詞及用法：

1. Feeling low：表示某人情緒低落或者心情不好。

例句：I've been feeling really low since my best friend moved away.（自從我最好的朋友搬走后，我的心情一直很低落。）

2. Going through a rough patch：表示某人處于困境或者遇到了困難。

例句：She's been going through a rough patch in her marriage, but things are getting better now.（她的婚姻出現了問題，但現在情況正在好轉。）

3. In a funk：表示某人心情不好或者處于低谷。

例句：Ever since she failed her exam, she's been in a funk and doesn't want to talk to anyone.（自從她考試不及格后，她一直心情很差，也不想和任何人說話。）

4. Down in the dumps：表示某人感到沮喪或者消沉。

例句：He's been down in the dumps ever since he lost his job, I hope things start looking up for him soon.（自從失業后，他一直感到沮喪，希望他能很快走出困境。）

5. Struggling：表示某人正在努力應對困難或者掙扎。

例句：I've been struggling with my mental health lately, but I'm trying to stay positive.（最近我的心理健康有些問題，但我在努力保持積極的態度。）