Books Are Not Paper and Rabbits Are Birds

Welcome to a post on what was probably the first linguistic oddity you encountered when learning Japanese.

In English, you can say three books or five cars and call it a day. The Japanese language uses counters (助数詞 / じょすうし) which are classifier words that match the thing you're counting. It’s as if English forced you to say "three-bound-volumes of books" and "five-machines of cars".

Why? This system comes from a mixture of native Japanese counting words (訓読み, kun’yomi) and readings borrowed from Chinese (音読み, on’yomi). They come together to make a functional if slightly eclectic system.

I will also bestow upon you my bullshit ways of remembering all these.

The General Counter: 〜つ

〜つ uses the native Japanese number system (up to 10):

ひとつ (1), ふたつ (2), みっつ (3), よっつ (4), いつつ (5), むっつ (6), ななつ (7), やっつ (8), ここのつ (9), とお (10).

This is why learners often feel like they are counting twice. The familiar いち, に, さん do not apply here.

It’s a useful safety net when you don’t know the specific counter, but you get brownie points for using all these other cool counters below.

People: 人

I remember this one because it kind of looks like a little leggy fella.

一人 (ひとり) and 二人 (ふたり) are the two irregular native forms you need to know.

三人 (さんにん), 四人 (よにん), 五人 (ごにん)… are regular.

Shape-Based Counters

〜個

Used for small, round, or compact things (apples, balls, sweets, units of measurement).

Irregular at: 一個 (いっこ), 六個 (ろっこ), 八個 (はっこ), 十個 (じゅっこ).

Otherwise: 〜こ.

This is one of the most flexible counters — if you’re unsure which counter to use, 〜個 is usually acceptable.

〜本

For long, thin objects (pens, bottles, umbrellas, trains). Things with a ratio of at least 1:2. I remember this one because it is the kanji for book but doesn't pertain to books.

Irregular at: 一本 (いっぽん), 三本 (さんぼん), 六本 (ろっぽん), 八本 (はっぽん), 十本 (じゅっぽん).

Otherwise: 〜ほん.

〜枚

For flat, thin objects (paper, plates, shirts). I remember this one because it kind of looks like a shirt.

Always regular: 〜まい.

〜冊

For bound volumes (books, notebooks). I remember this one because it looks like books on a bookshelf.

Irregular but predictable number pronunciations at 八冊 (はっさつ) and 十冊 (じゅっさつ).

Otherwise: 〜さつ.

Animals

〜匹

For small animals (cats, dogs, fish). I remember this one because it is a box and small animals fit in boxes.

Irregular at: 一匹 (いっぴき), 三匹 (さんびき), 六匹 (ろっぴき), 八匹 (はっぴき), 十匹 (じゅっぴき).

Otherwise: 〜ひき.

〜頭

For large animals (horses, cows, elephants). Always regular: 〜とう.

I remember this one because it is the kanji for head and historically cattle was referred to as heads of cattle. Which is also how this counter came about, it turns out.

〜羽

For birds - and rabbits, historically reclassified as birds due to, I believe, tax reasons. I remember this one because it looks like two bunny ears.

Always regular: 〜わ.

Wah.

Machines and Buildings

〜台

For machines, vehicles, furnitures, large instruments, and whole cakes. I remember this one because the sheer quantity of things it is associated with is silly.

Always regular: 〜だい.

〜階

For floors of a building. I don't really remember this one because I haven't used it as much. The beginning looks like an eszett which is memorable I guess.

Number shortens at 六階 (ろっかい) and 十階 (じゅっかい).

Otherwise regular: 〜かい.

Time (in one sense or another)

〜回

For repetitions or occurrences. I remember this one because the square repeats itself. If you increase the font size enough you can see another tiny square inside it (real).

Irregular conjugation at 1, 6, and 10. Otherwise regular: 〜かい.

〜歳

For age. I remember this one because it looks like a funny birthday cake.

Irregular conjugation at 1, 8, and 10. Otherwise regular: 〜さい.

Fun fact, they found a simpler kanji for this because this one was too hard to write. 才 is also valid, but 歳 is more correct.

Time and date

Words like 年 (ねん), 月 (つき/がつ), 日 (か/にち), 時間 (じかん), 時 (じ) and 分 (ふん) are also counters. Woah.

One relevant distinction to make is that 時間 is for literally saying "hours" and 時 is more like "o'clock".

Years, hours (elapsed) and hours (telling the time) are always regular.

Months

I don't even really know how I'm supposed to explain this but when you specify a month in the context of its number in the calendar then it's always regular (がつ) with Sino-Japanese readings.

When you use months in a more descriptive or poetic context you use native readings with つき.

When you are talking about something taking a number of months you use かげつ.

Days of the month

The readings for the day of the month are mostly native numbers, not Sino-Japanese, and are irregular for certain days:

Date	Reading	Notes
1	ついたち	special historical reading
2	ふつか	native irregular
3	みっか	native irregular, small っ appears
4	よっか	native irregular, small っ appears
5	いつか	native irregular
6	むいか	native irregular, small っ appears
7	なのか	native irregular
8	ようか	native irregular
9	ここのか	native irregular
10	とおか	native irregular
11–19	[11–19日] にち	regular Sino-Japanese reading added to native counting
20	はつか	historical/fixed irregular
21–31	[21–31日] にち	regular pattern continues

Minutes

Minutes use Sino-Japanese numbers, but some numbers trigger phonetic changes:

Number	Reading	Notes
1	いっぷん	small っ inserted
2	にふん	regular
3	さんぷん	p → unvoiced shift
4	よんふん	regular
5	ごふん	regular
6	ろっぷん	small っ inserted
7	ななふん	regular
8	はっぷん	small っ inserted
9	きゅうふん	regular
10	じゅっぷん	small っ inserted

Other interesting counters

〜杯

For glasses/cups. I remember this one because it's kind of like the flat things counter but flatter.

Irregular at 一杯 (いっぱい), 三杯 (さんばい), 六杯 (ろっぱい), 十杯 (じゅっぱい).

Otherwise 〜はい.

〜着

For clothing. I remember this one because it's also used for 着く which is to arrive, and I like it when clothes arrive in the post.

Irregular at 一着 (いっちゃく), 八着 (はっちゃく), 十着 (じゅっちゃく).

Otherwise 〜ちゃく.

〜話

For stories or episodes. Useful for discussing anime. I remember this one because it is the kanji for story. Always regular.

I also have other counters, but you can probably find them on Tofugu in this nifty article. And also I want to blow my brains clean out after the time section.