Ppm.
[医] 兆比率(百万分之几)
🗣️ 情景例句
You should save some money in case of urgent need.
你应该存点钱以备不时之需。
We pitied the family in their sudden unhappiness.
那家人遭受突然的不幸，我们深感同情。
No, they aren't. They're their books.
不，不是我的。这些是他们的书。