In English, you can count almost anything with the same numbers: two books, two pens, two cats. Japanese doesn't work that way. The number changes form depending on what's being counted, through a system of counter words attached directly to the number.
How counters work
A counter is a suffix added to a number that identifies the category of object being counted, usually based on its shape or type. Instead of saying "three" on its own, Japanese says "three-[counter]," and the counter changes depending on whether you're counting flat objects, long thin objects, small animals, people, or something else entirely.
| Counter | Used for | Example |
|---|---|---|
| 枚 (mai) | Flat, thin objects: paper, plates, shirts, tickets | 紙が3枚 (three sheets of paper) |
| 本 (hon) | Long, thin objects: pens, bottles, trees, umbrellas | ペンが2本 (two pens) |
| 匹 (hiki) | Small animals: cats, dogs, insects, fish | 猫が1匹 (one cat) |
| 頭 (tou) | Large animals: cows, horses, elephants | 牛が2頭 (two cows) |
| 人 (nin) | People | 学生が4人 (four students) |
| 個 (ko) | Small, roughly round or cube-shaped objects: apples, boxes, eggs | りんごが5個 (five apples) |
| 台 (dai) | Machines and vehicles: cars, computers, bicycles | 車が1台 (one car) |
| 冊 (satsu) | Bound objects: books, magazines, notebooks | 本が3冊 (three books) |
The reading changes depending on the number
To make this harder, the pronunciation of some counters shifts depending on which number precedes them, due to sound changes in Japanese phonology. 本 (hon) is read differently after 1, 3, 6, 8, and 10 than it is after 2, 4, 5, 7, and 9.
The counter character stays the same; the pronunciation shifts.
What happens when you don't know the right counter
There's a fallback: the native Japanese number system (ひとつ, ふたつ, みっつ...) works as a generic counter for up to ten of almost anything, when you're not sure which specific counter applies. It sounds slightly less precise than using the correct specific counter, but it's universally understood and grammatically correct.
Ringo ga mittsu arimasu. There are three apples, using the generic counter instead of 個.
Why this matters for translation
When translating from Japanese, the counter itself usually doesn't need to appear in the English output, since English just uses the bare number. The risk runs the other direction: translating English into Japanese, where a tool has to correctly guess which counter applies to the object being described. Machine translation generally handles common counters like 人 (people) and 個 (small objects) reliably, but less common categories, like counters for specific cultural items, sometimes get the generic counter substituted in instead of the precise one a native speaker would choose.
Translate a sentence with numbers and see which counter gets used.
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