Introduction
第 (dì) is the standard way to make an ordinal — 第三 (dì sān) is "third". But floors, room numbers, bus routes, weekdays and dates skip it entirely and use the bare number: 三楼 (sān lóu) is the third floor, not three floors.
Overview
Structure: Number + Measure Word (no 第 (dì))
| Pattern | Example | Translation |
|---|---|---|
| Floor | 三楼 (sān lóu) | the third floor |
| Room | 五号房间 (wǔ hào fángjiān) | room five |
| Bus route | 三路车 (sān lù chē) | the number 3 bus |
| Date | 五月三号 (wǔ yuè sān hào) | the third of May |
| With 第 | 第三个人 (dì sān ge rén) | the third person |
Anything with a fixed number of its own drops 第 (dì):
- 三楼 (sān lóu)、五号 (wǔ hào)、三路车 (sān lù chē)、星期三 (xīngqīsān)、三月 (sān yuè) — all bare.
- Ranking and order in a queue keep 第 (dì): ✓ 第三个人 (dì sān ge rén) — the third person.
- This is where the trap is: 三楼 (sān lóu) is the third floor, but 三个楼 (sān ge lóu) is three buildings.
- The difference is the measure word. 楼 (lóu)、号 (hào)、路 (lù) already name a numbered slot; 个 (ge) just counts.
Examples
我住在三楼。
Wǒ zhù zài sān lóu.
I live on the third floor.
他在五号房间。
Tā zài wǔ hào fángjiān.
He's in room five.
你坐三路车就到了。
Nǐ zuò sān lù chē jiù dào le.
Take the number 3 bus and you're there.
今天是五月三号。
Jīntiān shì wǔ yuè sān hào.
Today is the third of May.
我们星期三见。
Wǒmen xīngqīsān jiàn.
See you on Wednesday.
他是第三个来的。
Tā shì dì sān ge lái de.
He was the third to arrive.
Usage Notes
- The everyday bare-number set: 楼 (lóu) floors, 号 (hào) numbers and dates, 路 (lù) bus routes, 班 (bān) classes, 楼 (lóu) and 单元 (dānyuán) in addresses.
- Weekdays and months are built this way too, which is why 星期三 (xīngqīsān) needs no 第 (dì) — though Sunday is the exception, 星期天 (xīngqītiān).
- Use 第 (dì) as soon as you mean a position in a sequence you are counting out: 第一次 (dì yī cì) — the first time.
- Asking which one takes 几 (jǐ), with no 第 (dì): 你住几楼？(Nǐ zhù jǐ lóu?) — which floor do you live on?
- When in doubt, ask whether the thing has a permanent number painted on it. If it does, drop 第 (dì).