X 是 ...，Y 是 ...
Reach for this when you want to lay out two parallel items side by side — 'X is ..., Y is ...'. It's the simplest way to spell out two reasons, two features, two roles in a clean A/B layout. Common when listing reasons ('first reason is..., second reason is...'), comparing people, or breaking a topic into named parts. The repeated 是 makes the parallel feel rhythmic and easy to follow.
Structure
[X] 是 [ITEM 1], [Y] 是 [ITEM 2]
...shì..., ...shì...
How to Think About It
Repetition is the point. Chinese loves parallel scaffolding — when two halves share the same shape, they feel weightier than the same content thrown into a single mixed sentence. Keep both 是 clauses similar in length and structure. If they drift in form, the listener loses the parallel feel. X and Y don't have to be people; they can be '第一' / '第二', '一个' / '另一个', or any two named slots.
Examples
第一个是我的哥哥, 第二个是我的弟弟。
Dì-yī gè shì wǒ de gēge, dì-èr gè shì wǒ de dìdi.
The first one is my older brother, the second is my younger brother.
一个原因是天气, 另一个原因是时间。
Yī gè yuányīn shì tiānqì, lìng yī gè yuányīn shì shíjiān.
One reason is the weather, another is timing.
我妈是医生, 我爸是老师。
Wǒ mā shì yīshēng, wǒ bà shì lǎoshī.
My mom is a doctor, my dad is a teacher.
Common Mistake
Learners use this for two unrelated facts, but the pattern works only when X and Y are on the same axis — both are reasons, both are features, both are people in the same role. Mixing categories breaks the parallel and the sentence sounds disjointed.
第一个原因是漂亮, 第二个是他姐姐很好。
第一个原因是漂亮, 第二个原因是便宜。
Don't Confuse With
一方面 ... 另一方面 ...
Two sides of the same situation, often complementary or in tension. X 是..., Y 是... is a clean list, no tension implied.
首先 ... 其次 ...
Ordered enumeration of points or steps. X 是..., Y 是... is also a list, but each slot gets a label (first, second / one, another) rather than a sequence word.
不是 X, 而是 Y
Replaces X with Y — only Y is true. X 是..., Y 是... lays out two true things in parallel; nothing is being replaced.
Practice
第一个原因 ___ 便宜, 第二个原因是好用。
Show answer
是
一个 ___ 我哥哥, 另一个是我朋友。
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是
Put in order: [第一 / 是 / 第二 / 大 / 是 / 便宜 / 个 / 个]
Show answer
第一个是大, 第二个是便宜。
Translate to Chinese: 'One advantage is the price, the other is the quality.'
Show answer
一个好处是价格, 另一个好处是质量。
Write one sentence listing two parallel reasons or features, using X 是 ..., Y 是 ....
Show answer
Example answer: 第一个原因是离家近, 第二个原因是工资好。 (The first reason is it's close to home, the second is the pay is good.)