A + 比 + B + Adjective
The basic Chinese comparison: 'A is more [adjective] than B.' Put A first, 比 in the middle, then B, then the adjective bare at the end. No copula, no 'than,' no 'more' — 比 alone does the comparing. From your first comparison sentence onward, this is the template you'll use for prices, sizes, ages, distances, and just about every 'X-er than Y' thought in Mandarin.
Structure
[A] 比 [B] [ADJECTIVE]
[A] bǐ [B] [ADJ]
How to Think About It
比 is the verb of comparison itself; the adjective on the right is just the dimension you're comparing along. That's why intensifiers like 很 or 非常 don't belong in front of the adjective in a 比 sentence — they'd make the comparison non-comparative. To add degree, attach a quantity to the right of the adjective: 高一点, 大三岁, 便宜很多.
Examples
中国比日本大。
Zhōngguó bǐ Rìběn dà.
China is bigger than Japan.
我妹妹比我小两岁。
Wǒ mèimei bǐ wǒ xiǎo liǎng suì.
My younger sister is two years younger than me.
这件衣服比那件便宜。
Zhè jiàn yīfu bǐ nà jiàn piányi.
This piece of clothing is cheaper than that one.
Common Mistake
Learners pad the adjective with 很 because they're used to 我很高. In a 比 sentence, 很 disappears — the comparison itself is the degree. Adverbs go after the adjective, as a measurement.
他比我很高。
他比我高。
Don't Confuse With
A 没有 B 那么 + Adjective
Use this for the negative direction ('A isn't as [adj] as B'). 比 has no clean negation — 不比 has a special 'not necessarily more' flavor, not a plain negative.
A 跟 B 一样 + Adjective
Pick 一样 when A and B are equal. 比 is strictly for unequal comparisons.
A 比较 + Adjective
比较 means 'relatively' or 'fairly' and stands alone with one subject. Use 比 only when you're naming a specific B to compare A against.
Practice
Fill in the blank: 飞机___火车快。
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比
Fill in the blank: 今天比昨天___。 (hotter)
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热
Arrange: 多 / 比 / 北京 / 上海 / 人
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上海比北京人多。
Translate to Chinese: His car is more expensive than mine.
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他的车比我的车贵。
Write a sentence using A 比 B + adj comparing two foods you like.
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面条比米饭好吃。