X 比 Y + Adj
Reach for this whenever you want to compare two things directly — 'X is more [adjective] than Y.' 比 sits between the two items being compared, then the adjective comes after. To say 'by how much,' tack the amount onto the end (X 比 Y 大三岁 — 'X is 3 years older than Y'). This is the workhorse comparison structure in Chinese.
Structure
[X] 比 [Y] [ADJ] (+ AMOUNT)
[X] bǐ [Y] [ADJ]
How to Think About It
Chinese drops the equivalent of English 'more' entirely. The adjective alone, sitting after 比, already means 'more so.' Do NOT add 更 or 很 in front of the adjective inside a 比 sentence — 'A 比 B 很大' is wrong because 比 already establishes the comparative force. The amount of difference goes after the adjective, not before: 大三岁, not 三岁大.
Examples
今天比昨天热。
Jīntiān bǐ zuótiān rè.
Today is hotter than yesterday.
他比我大三岁。
Tā bǐ wǒ dà sān suì.
He's three years older than me.
这个苹果比那个甜得多。
Zhège píngguǒ bǐ nàge tián de duō.
This apple is much sweeter than that one.
Common Mistake
Learners add 很 before the adjective ('A 比 B 很高'), copying the standard 很 + adjective pattern. Inside a 比 sentence, 很 is forbidden — the comparison itself already provides the intensity.
我哥哥比我很高。
我哥哥比我高。
Don't Confuse With
X 没有 Y + Adj
Negation of comparison: 'X is not as [adj] as Y.' Use 没有 instead of 不比 for most negative comparisons — 不比 sounds odd in many contexts.
X 跟 Y 一样 + Adj
Use 跟...一样 when X and Y are equal on the adjective. 比 only works when there's a difference.
X 更 + Adj
Use 更 when Y is implied from context, not stated. 比 names both items explicitly; 更 floats by itself ('even more [adj]').
Practice
我 ___ 我弟弟高。
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比
这本书比那本书 ___。 (interesting)
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有意思
Arrange: 北京 / 比 / 冷 / 上海 / 冬天
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北京冬天比上海冷。
My phone is more expensive than his by 500 yuan.
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我的手机比他的贵五百块。
Use X 比 Y + Adj to compare two cities or two foods.
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上海的夏天比北京的更潮湿。