HSK 4
X是X，Y是Y
X shì X ， Y shì Y
X is X, Y is Y (a clear distinction)
Explanation
The structure X是X，Y是Y (X shì X, Y shì Y) is used to emphasize that two things/people/moments are DIFFERENT and must be clearly distinguished, not conflated or confused. 是 (shì) here is the verb "to be".
repeat the same word on both sides of 是 — X + 是 + X，Y + 是 + Y.
他是他，我是我 he is he, I am I. It is usually followed by a sentence demanding a distinction or stating a consequence, such as 这要分清楚 this must be clearly distinguished.
when you want to clearly separate two matters, to stop the listener from lumping them together or using one matter as an excuse to skip the other (as in 昨天是昨天，今天是今天 — yesterday's matter is irrelevant, today you still have to hand in the assignment).
Vietnamese learners easily translate it machine-like into "X thì là X", which sounds stiff; in fact this is an emphatic frame for "keeping things crystal clear", and you must keep the repeated pattern X是X，Y是Y to get the right nuance.
Examples
One is one, two is two — this has to be kept clearly distinct.
He is he, I am I; it's perfectly normal for us to have different opinions.
Yesterday is yesterday, today is today — you have to hand in your homework.
Practice
Test your understanding with a quick quiz
Learn “X是X，Y是Y” effectively
The grammar point “X是X，Y是Y” (X is X, Y is Y (a clear distinction)) is one of the key structures at HSK 4. To use it fluently, you need to understand the contexts where it's used and practice regularly.
Study tip: read the examples aloud many times to build a natural reflex. Then try making your own sentences for your own situations. Use the audio button to hear and practice accurate pronunciation.
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