In Japanese you cannot count with a number alone. You add a counter that matches the kind of thing you count, a little like 'two sheets of paper' in English. The quantity usually comes after the noun and its particle, right before the verb: 切手を二枚買います. Some counters change their sound with some numbers, so the readings must be learned: 一本 is いっぽん, 三本 is さんぼん, 六本 is ろっぽん, and one person and two people are ひとり and ふたり.
§1Structure
Number + counter. 〜つ: things in general, 1 to 10 (ひとつ, ふたつ, みっつ … とお). 〜人 (にん): people (ひとり, ふたり, さんにん, よにん). 〜枚 (まい): thin, flat things (paper, stamps, shirts). 〜台 (だい): machines and vehicles. 〜本 (ほん): long, thin things (pens, bottles, umbrellas). 〜回 (かい): number of times. Usual position: Noun + が／を + quantity + verb (りんごを三つ買います). No particle comes after the quantity. Another pattern: quantity + の + Noun (二台の車). Question words: いくつ, 何人, 何枚, 何台, 何本, 何回.
§2Examples
りんごを三つ買いました。
りんごをみっつかいました。
I bought three apples.
教室に学生が五人います。
きょうしつにがくせいがごにんいます。
There are five students in the classroom.
切手を二枚ください。
きってをにまいください。
Two stamps, please.
コピーは十枚じゃありません。二十枚お願いします。
コピーはじゅうまいじゃありません。にじゅうまいおねがいします。
It's not ten copies. Twenty copies, please.
「家族は何人ですか。」「四人です。」
「かぞくはなんにんですか。」「よにんです。」
"How many people are there in your family?" "Four."
家の前に二台の車が止まっています。
いえのまえににだいのくるまがとまっています。
Two cars are parked in front of the house.
この映画は二回見ました。
このえいがはにかいみました。
I have seen this movie twice.
ボールペンを六本買った。
ボールペンをろっぽんかった。
I bought six ballpoint pens.
§3Common mistakes
- Putting the quantity in the wrong place or adding an extra particle: ×三つをりんご買いました, ×りんごを三つを買いました. The usual order is noun + particle + quantity + verb, with no particle after the quantity: りんごを三つ買いました. Vietnamese speakers should be careful, because 'ba quả táo' puts the number first.
- Reading the numbers without the sound changes: ×いちにん, ×ににん, ×よんにん for people (correct: ひとり, ふたり, よにん), and ×いちほん, ×さんほん, ×ろくほん for long things (correct: いっぽん, さんぼん, ろっぽん). 〜枚 and 〜台 do not change: いちまい, さんだい.
- Using one counter for everything: ×学生が三ついます, ×紙を二本ください. People take 〜人 (学生が三人います), and thin, flat things take 〜枚 (紙を二枚ください). 〜つ is a useful general counter for things, but it is not used for people, and it only goes up to ten (とお).
§4How it's different from similar grammar
- Noun を quantity vs. quantity の Noun
- Both are correct. りんごを三つ買いました is the usual way to say how many, and it is the pattern that N5 tests. 三つのりんごを買いました is less common in conversation. It treats the things as one group and is seen more often in writing and in stories: 二人の子どもが公園で遊んでいます (Two children are playing in the park). In the first pattern no particle follows the quantity; in the second pattern の is needed.
- period + に + 〜回 (times per period)
- 〜回 alone says how many times something happened: この映画は二回見ました (I have seen this movie twice). When you add a period + に before it, it says how often: 一週間に二回、日本語を勉強します (I study Japanese twice a week). Here に means 'per'. Do not put に after 〜回 itself: ×二回に見ました.
§5How this shows up on the JLPT
Counters appear in every part of N5. In the kanji and vocabulary section, you choose the reading of words such as 一本, 三本, 一人 and 二人, so learn the sound changes. In Mondai 1 of the grammar section, you choose the right counter for the noun (paper → 枚, car → 台, pen → 本) or the right question word (何人, 何枚, いくつ). In Mondai 2 (sentence ordering), the quantity goes between the particle and the verb: りんご・を・三つ・買いました. In listening, numbers and counters are said quickly in shopping scenes, so practice hearing いっぽん, さんぼん and ろっぽん.
§6Quick check (3 questions)
1. Choose the counter that fits the blank: はがきを五＿＿ください。
はがきをご＿＿ください。
2. How do you read 三本 in this sentence? えんぴつが三本あります。
えんぴつが＿＿あります。
3. Which sentence correctly says 'I ate two eggs'?