买 (mǎi) "to buy" and 卖 (mài) "to sell" are the single most instructive pair in beginner Chinese, because they teach you — in one stroke — that tone is meaning, not decoration. The two words are near-identical: on paper, 卖 is just 买 with a 十 ("ten") stacked on top; in speech, the only thing separating "I'm buying" from "I'm selling" is a third tone (mǎi, dipping low) versus a fourth tone (mài, falling sharp). There is no context-based safety net here — 我买 and 我卖 are both perfectly grammatical, so a slipped tone doesn't produce nonsense, it produces the opposite transaction. That is exactly why this pair is worth drilling until it's automatic.
Sense 1: 买 (mǎi) — buy
买 is transitive: you buy something. The object is rarely omitted — 买 almost always drags a noun behind it (买东西, 买菜, 买票).
我想买一件衣服。
wǒ xiǎng mǎi yí jiàn yīfu
I want to buy a piece of clothing. — 买 + measure phrase 一件衣服.
周末我要去超市买点儿东西。
zhōumò wǒ yào qù chāoshì mǎi diǎnr dōngxi
On the weekend I'm going to the supermarket to buy some stuff. — 买东西 'buy things / go shopping'.
妈妈每天早上去菜市场买菜。
māma měitiān zǎoshang qù càishìchǎng mǎi cài
Mom goes to the market every morning to buy groceries. — 买菜 'buy food/groceries'.
Sense 2: 卖 (mài) — sell
卖 is the mirror image — the goods leave you and money comes in. The subject is the seller; the thing sold is the object (卖水果, 卖二手书).
他在网上卖二手书。
tā zài wǎng shàng mài èrshǒu shū
He sells secondhand books online. — 卖 + object 二手书.
这儿卖不卖邮票？
zhèr mài bu mài yóupiào
Do they sell stamps here? — 卖不卖, an A-not-A question.
不好意思，票已经卖完了。
bù hǎoyìsi, piào yǐjīng màiwán le
Sorry, the tickets are already sold out. — 卖完 'sell to completion', the resultative for 'sold out'.
The tone contrast is the whole point
Say the pair out loud back to back. 买 (mǎi) dives down and rises again — the long, low, "dipping" third tone. 卖 (mài) drops like a hammer, short and hard — the fourth tone. If you flatten mǎi into a fall, a native speaker hears 卖, and your "I'd like to buy this" becomes "I'm selling this." The meanings are so cleanly opposed that the listener can't rescue you from context.
我买，你卖，咱们成交。
wǒ mǎi, nǐ mài, zánmen chéngjiāo
I buy, you sell — it's a deal. — the tone is the only thing distinguishing the two roles.
Sense 3: the affordability potential — 买得起 / 买不起
Stitch the potential complement 起 (qǐ, "manage / afford") onto 买 and you get a phrase English has to say with a whole verb, "afford": 买得起 (mǎi de qǐ) "can afford", 买不起 (mǎi bu qǐ) "can't afford". This is not the same as 能买 "be allowed / able to buy" — 起 specifically asks whether your wallet can reach the price.
这个牌子的包我买不起。
zhège páizi de bāo wǒ mǎi bu qǐ
I can't afford a bag of this brand. — 买不起 'can't afford'.
努力工作，将来买得起房子。
nǔlì gōngzuò, jiānglái mǎi de qǐ fángzi
Work hard and you'll be able to afford a house someday. — 买得起 'can afford'.
买卖 (mǎimai) — business
Put the two verbs together, buy-then-sell, and you get the noun 买卖 (mǎimai, second syllable neutral) "business, trade, a deal" — a nice window onto how Chinese builds abstractions out of paired opposites (compare 大小 "size", 多少 "amount").
他辞职了，自己做点小买卖。
tā cízhí le, zìjǐ zuò diǎn xiǎo mǎimai
He quit his job to run a small business of his own. — 做买卖 'do business'.
Key collocations
| Phrase | Pinyin | Meaning |
|---|---|---|
| 买东西 | mǎi dōngxi | buy things, go shopping |
| 买菜 | mǎi cài | buy groceries |
| 买票 | mǎi piào | buy a ticket |
| 买单 | mǎidān | pay the bill (restaurant) |
| 买得起 / 买不起 | mǎi de qǐ / mǎi bu qǐ | can / can't afford |
| 卖东西 | mài dōngxi | sell things |
| 卖水果 | mài shuǐguǒ | sell fruit |
| 卖完 / 卖光 | màiwán / màiguāng | sold out |
| 甩卖 | shuǎimài | clearance sale |
| 买卖 | mǎimai | business, trade, a deal |
Grammar notes
Both verbs take 了, 过, and complements freely: 买到 (mǎidào) "manage to buy / get hold of", 卖完 (màiwán) "sell out", 卖给 (mài gěi) "sell to". To name the person you buy from or sell to, lean on a coverb — 卖给他 "sell it to him", 从他那儿买 "buy it from him". For the money-side verb that pairs with buying, see 花 (spend); for swapping and returning goods, see 换 (change / exchange). The affordability potential 买不起 is one instance of the wider potential complement with 得起/不起.
Common Mistakes
1. Flipping the tone — buying when you mean selling. This is the cardinal error. A falling tone on 买 turns it into 卖.
❌ 我昨天卖了一台新电脑。
Wrong verb if you're the customer — 卖 is SELL. If you bought it, the third-tone 买 is what you need.
✅ 我昨天买了一台新电脑。
wǒ zuótiān mǎi le yì tái xīn diànnǎo
I bought a new computer yesterday.
2. Writing the wrong character. On paper the giveaway is the 十 on top: 卖 (with 十) = sell, 买 (no 十) = buy.
❌ 水果店的招牌上写着「买苹果」。
A shop sign advertising its goods should say 卖 (sell) — 买苹果 reads 'buy apples', as if the shop were the customer.
✅ 水果店的招牌上写着「卖苹果」。
shuǐguǒ diàn de zhāopái shàng xiězhe mài píngguǒ
The fruit shop's sign reads 'apples for sale'.
3. Using 不能买 for "can't afford". 不能买 means "not allowed / not able to buy"; the money sense needs 买不起.
❌ 这辆车太贵了，我不能买。
This says 'I'm not permitted/able to buy it' — for 'can't afford it', use the potential 买不起.
✅ 这辆车太贵了，我买不起。
zhè liàng chē tài guì le, wǒ mǎi bu qǐ
This car is too expensive — I can't afford it.
4. Saying 没有 for "sold out". "Sold out" is a result of selling, so it takes the resultative 卖完了 / 卖光了, not a bare 没有.
❌ 对不起，这个没有了，卖了。
Unclear — a bare 卖了 doesn't say the stock ran out. 'Sold out' is 卖完了 / 卖光了.
✅ 对不起，这个卖完了。
duìbuqǐ, zhège màiwán le
Sorry, this one is sold out.
Key Takeaways
- 买 (mǎi, third tone, dipping) = buy; 卖 (mài, fourth tone, falling) = sell. The tone is the meaning — a slip flips the transaction.
- On paper: 卖 = 买 + 十 on top. The "ten" marks the seller.
- Both are transitive and almost always carry an object: 买东西, 卖水果.
- Affordability lives in the potential 起: 买得起 = can afford, 买不起 = can't (≠ 不能买).
- "Sold out" = 卖完了 / 卖光了; "business / a deal" = the paired noun 买卖 (mǎimai).
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- 花 (huā) — to spend (money / time)HSK 3 — 花 (huā) is one verb where English needs two: it 'spends' both money (花钱) and time (花时间). Learn its two frames — 花 + amount and the cost frame 事 + 花 + 我 + amount — and don't confuse it with 用 (use) or the homograph 花 'flower'.
- 换 (huàn) — change / exchange / swapHSK 3 — 换 (huàn) is 'swap one thing out for another' — 换钱, 换衣服, 换工作, 换乘. The A-for-B frame uses 换成. Keep it distinct from 改 (alter the same thing) and 变 (transform on its own).