一回事

一回事 [yī huí shì]

1. ■ （同一件事） one and the same (thing):

咱俩说的是一回事。 We were talking about the same thing.

他不懂水和H₂O分子式是一回事。 He didn't know that water and H₂O are one.

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常用词组

1. ■ （一方面） one thing:

说是一回事， 做又是一回事。 Talking is one thing, doing is another.