一、用作形容词
1. clean 的用法
clean 用作形容词时意为“干净的”“清洁的”等。如：
Apply the paint with a clean brush. 用干净的刷子涂油漆。
Cats should always have access to fresh, clean water. 猫应该总能喝到新鲜、干净的水。
Having clean hands is one of the cardinal rules when preparing food. 做饭前首先要把手洗干净。
The cut will heal up in a few days if you keep it clean and dry. 这个伤口只要保持清洁干爽，过不了几天就会愈合。
It’s clean and well-located, but best of all, it’s affordable. 那里很干净，地段也好，而且更不错的是，价格也承受得起。
2. cleanly 的用法
cleanly 用作形容词时 意为“(习惯上)爱干净的”。如：
Cats are cleanly animals. 猫是爱清洁的动物。
二、用作副词
两者都可用作副词，但词义不同：
1. clean 的用法
clean 意为“完全地”“彻底地”。通常连用的词语有动词forget，介词 through, over 等，副词 away, out 等。如：
The thief got clean away. 那小偷已逃之夭夭。
The bullet went clean through his shoulder. 子弹射穿了他的肩膀。
I clean forgot about calling him. 我把给他打电话的事忘得一干二净。
Sorry, I clean forgot (=completely forgot) your birthday. 对不起，我完全忘了你的生日。
I clean forgot that I was supposed to be meeting Lucy last night. 昨晚我本来应该跟露西见面的，结果我忘得一干二净。
He’s been cheating his customers for years, and getting clean away with it. 他欺骗顾客多年，还一点事都没有。
2. cleanly 的用法
cleanly 用作副词时意思是“利索地；整齐地；诚实地，清白地”。如：
The boat moved cleanly through the water. 小船在水面上轻快地行进。
The branch snapped cleanly in two. 树枝啪的一下断成两截。
Cut the stem cleanly, just beneath a leaf joint. 把茎切整齐点，正好切在叶根下。
The election campaign was not conducted very cleanly. 竞选活动搞得有点不清不白。