Floors, Grades & Ordinal Contexts (二楼, 三年级) | Chinese (Mandarin) Grammar

English has one all-purpose way to build ordinals — you stick "-th" (or "-st/-nd/-rd") on the number: second floor, third grade, room five. Chinese has a general ordinal marker too, 第 (dì, as in 第二 "the second"), but a large group of everyday "position" words simply don't use it. Instead the bare cardinal sits in front of the noun and is the position: 二楼 (èr lóu) "second floor," 三年级 (sān niánjí) "third grade," 五号 (wǔ hào) "number five." These are fixed slots where the number labels a rung in a fixed series, and two things follow from that: you omit 第, and you use 二 (not 两), because a label is never a count.

The number is a label, so no 第 and always 二

Whenever a number names a known position in a standing series — the floors of a building, the grades of a school, the numbered classes or windows or subway lines — Chinese treats it like a name tag. You don't wrap it in 第, and because it labels rather than counts, "two" is 二, the digit, never 两 the count-word.

Series	Form	Pinyin	Meaning
floor	二楼	èr lóu	the 2nd floor
floor (formal)	三层	sān céng	the 3rd floor
school grade	三年级	sān niánjí	3rd grade
class/section	二班	èr bān	Class 2
number (window, size, ticket)	五号	wǔ hào	No. 5
subway line	一号线	yí hào xiàn	Line 1
building	三号楼	sān hào lóu	Building 3

洗手间在二楼，电梯在那边。

xǐshǒujiān zài èr lóu, diàntī zài nàbiān

The restroom is on the second floor; the elevator's over there. (neutral) — 二楼, a floor label, so 二 not 两.

我儿子今年上三年级了。

wǒ érzi jīnnián shàng sān niánjí le

My son is in third grade this year. (informal) — 三年级, no 第.

请到五号窗口办理。

qǐng dào wǔ hào chuāngkǒu bànlǐ

Please go to window number 5 to take care of it. (formal) — 号 labels a numbered position.

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Test: could you point at a fixed list and say "that one, position N"? Floors, grades, classes, gates, lines, building numbers, clothing sizes — all labels. Labels never take 两; it's 二楼, 二班, 二号 every time. Save 两 for when you're actually counting objects.

Label vs. count: 二楼 but 两层楼

The sharpest way to feel the rule is to put the label right next to the count. 二楼 (èr lóu) is the second floor — a position. 两层楼 (liǎng céng lóu) is two floors — a quantity you counted, so it uses 两 plus the measure word 层. Same building, two completely different jobs for "two."

我住二楼，他住三楼，我们就差一层。

wǒ zhù èr lóu, tā zhù sān lóu, wǒmen jiù chà yì céng

I live on the second floor, he's on the third — we're just one floor apart. (informal) — labels 二楼/三楼, but the gap 一层 is counted.

电梯坏了，我爬了两层楼才到家。

diàntī huài le, wǒ pá le liǎng céng lóu cái dào jiā

The elevator was broken, so I climbed two flights to get home. (informal) — 两层楼, a counted quantity, takes 两.

这栋楼一共有二十层。

zhè dòng lóu yígòng yǒu èrshí céng

This building has twenty floors in total. (neutral) — counting the floors, 二十层.

Note the last one: 二十层 uses 二 inside 二十 because there the "two" is just the tens digit — that's the same logic explained on the 二 vs 两 page. The takeaway is stable: naming the floor you're on → 二楼; counting how many floors → 两层.

The everyday series: grades, classes, gates, sizes

Once you recognise the pattern, it turns up everywhere in daily life, and Chinese school culture in particular is built on it. Primary school runs 一年级 to 六年级; then junior high uses 初一/初二/初三 (chū yī, chū èr, chū sān), senior high 高一/高二/高三, and university 大一/大二/大三/大四. Within a grade, students are sorted into numbered classes — 二班, 三班 — and the bigger unit comes first: 三年级二班 (Grade 3, Class 2).

他在三年级二班，我女儿在一班。

tā zài sān niánjí èr bān, wǒ nǚ'ér zài yì bān

He's in Grade 3, Class 2, and my daughter's in Class 1. (informal) — grade before class, both bare cardinals.

我上大二，明年就该实习了。

wǒ shàng dà èr, míngnián jiù gāi shíxí le

I'm a second-year at uni; next year I'll have to do an internship. (informal) — 大二, sophomore, no 第.

这件衣服有点小，有没有大号的？

zhè jiàn yīfu yǒudiǎn xiǎo, yǒu méiyǒu dà hào de?

This one's a bit small — do you have a large? (informal) — sizes are 大号/中号/小号 or numbered 号.

去人民广场坐地铁一号线最方便。

qù Rénmín Guǎngchǎng zuò dìtiě yí hào xiàn zuì fāngbiàn

Taking Line 1 is the easiest way to People's Square. (informal) — subway lines use 号线, read with the plain number.

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For British English speakers: mainland China numbers floors the American way. The floor you enter from the street is 一楼 (the "first floor," = British "ground floor"), so China's 二楼 is the British "first floor." When someone says 三楼, count from the street level, not from the British system, or you'll knock on the wrong door.

One cultural quirk worth knowing: many Chinese buildings skip 四楼, because 四 (sì) sounds close to 死 (sǐ, "death"). You may step out of an elevator and find the buttons jump from 三楼 to 五楼, or that 四 is relabelled. The number is being avoided precisely because it's a fixed label people read aloud.

这栋楼没有四楼，直接从三楼跳到五楼。

zhè dòng lóu méiyǒu sì lóu, zhíjiē cóng sān lóu tiào dào wǔ lóu

This building has no fourth floor — it jumps straight from three to five. (neutral) — 四 avoided for sounding like 死.

Common Mistakes

1. Using 两 for a floor, grade, or class label. Positions are labels, so "two" is 二, never 两.

❌ 他住在两楼。

Incorrect — 'second floor' is a label: 二楼, not 两楼.

✅ 他住在二楼。

tā zhù zài èr lóu

He lives on the second floor.

2. Adding 第 to these set phrases. 二楼 and 三年级 already carry the ordinal sense; wrapping them in 第 sounds wrong.

❌ 我在第三年级。

Unnatural — the set phrase omits 第: just 三年级.

✅ 我在三年级。

wǒ zài sān niánjí

I'm in third grade.

3. Using 二 when you're actually counting floors. Once it's a quantity with 层, switch to 两.

❌ 这栋楼有二层。

Incorrect — counting floors needs 两 + 层: 两层.

✅ 这栋楼有两层。

zhè dòng lóu yǒu liǎng céng

This building has two floors.

4. Putting the smaller unit first. The larger category (grade) comes before the smaller (class).

❌ 二班三年级

Wrong order — the grade comes first: 三年级二班.

✅ 三年级二班

sān niánjí èr bān

Grade 3, Class 2.

Key Takeaways

A number that labels a fixed position — floor, grade, class, gate, size, subway line — takes the bare cardinal with no 第: 二楼, 三年级, 二班, 五号, 一号线.
These labels always use 二, never 两, because a label is not a count: 二楼 (the 2nd floor) vs. 两层楼 (two floors, counted).
Chinese school levels stack as 一–六年级 → 初一/二/三 → 高一/二/三 → 大一/二/三/四; the grade is named before the class (三年级二班).
Mainland floors follow the American system: street level is 一楼, so China's 二楼 = British "first floor."
Buildings often skip 四楼 because 四 echoes 死 ("death") — proof these numbers are read as spoken labels.

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