Build numbers from a few parts: Base 10 & the myriad system (万)

Master the logical architecture of Japanese numbers: combine ten basic digits to reach 99, handle irregular phonetics in hundreds and thousands, and master the 4-digit myriad shift at 10,000 (万).

Unit 5· Numbers, Counters & Time(Part 1 of 13)JLPTN5

Positional Number System: Building Tens, Hundreds & Thousands

multiplier digit

base unit: tens

ones place

copula

sanjuugo desu

It is 35 (literally: three-tens five).

Tens Construction (Multiplier + 十) vs Teens (十 + Digit)

Micro-Shift

全部で三十あります。

Multiplying tens: Digit precedes 十 (さん + じゅう = 30)There are thirty in all.

To say 30, place the multiplier before 10: 三 + 十 (さんじゅう).

Example Sentences

一番(いちばん)number one 好(す)きlike
It's my favorite
Word Details →
十(じゅう)ten まで数(かぞ)えてcount
Count to ten
Word Details →

Mental Model: The Transparent Lego System (Base 10)

Unlike European languages with historical oddities like “eleven,” “twelve,” or French “quatre-vingts” (four-twenties), Japanese numbers are built from pure mathematical Lego blocks:

1 to 10: 一(いち), 二(に), 三(さん), 四(よん / し), 五(ご), 六(ろく), 七(なな / しち), 八(はち), 九(きゅう / く), 十(じゅう).
11 is simply 10 + 1: 十一(じゅういち).
20 is 2 × 10: 二十(にじゅう).
99 is (9 × 10) + 9: 九十九(きゅうじゅうきゅう).

The Critical Threshold: The 4-Digit Myriad System (万)

The single biggest stumbling block for English speakers is large numbers:

Western Counting Groups by 1,000s (3 Zeros): Thousand (1,000) → Million (1,000,000) → Billion (1,000,000,000).
Japanese Counts Strictly by 10,000s (4 Zeros / 万(まん)):
10,000 is not ten-thousand; it has its own base unit: 一万(いちまん).
100,000 is 10 ten-thousands: 十万(じゅうまん).
1,000,000 is 100 ten-thousands: 百万(ひゃくまん).
10,000,000 is 1,000 ten-thousands: 千万(いっせんまん).
100,000,000 introduces the next 4-zero threshold: 一億(いちおく) (10,000 × 10,000).

The Irregular Phonetic Shifts in Hundreds and Thousands

When counting hundreds (百(ひゃく)) and thousands (千(せん)), several numbers cause phonetic sound mutations (gemination or voicing):

Hundreds (百(ひゃく)): 100 is bare 百(ひゃく) (no いち) · 300 is 三百(さんびゃく) (byaku) · 600 is 六百(ろっぴゃく) (pyaku) · 800 is 八百(はっぴゃく) (pyaku).
Thousands (千(せん)): 1,000 is bare 千(せん) (no いち) · 3,000 is 三千(さんぜん) (zen) · 8,000 is 八千(はっせん) (pause + sen).

Currency and Numbers in Daily Life

When attaching the currency counter 円(えん) (yen): 100円(ひゃくえん) (100 yen) · 1,000円(せんえん) (1,000 yen) · 10,000円(いちまんえん) (10,000 yen — notice that 万 must take いち in front: 一万円, never bare *万円!).

Conversation

In Dialogue

Sensei
教科書の四十五(よんじゅうご)ページを開いてください。
Please open page 45 of your textbook.
Student
はい、開きました！どの問題を読みますか？
Yes, opened! Which problem should we read?

Tips and Common Traps

Hana· Key point
Two counting lineages: Japanese uses Sino-Japanese numbers (一, 二, 三...) for arithmetic, clock hours, and measurements, and native Japanese words (ひとつ, ふたつ, みっつ...) for general physical items up to ten.
Maru· Common trap
Unlucky homophones: 四 can be read し (shi) or よん (yon). Because し sounds identical to 死 (death), よん is preferred in daily life! Similarly, 九 is often read きゅう (kyuu) to avoid sounding like 苦 (ku = suffering)!

Quick Check

47は日本語(にほんご)で「___」と読(よ)みます。47 is read as ‘...’ in Japanese.

Select the standard everyday reading for the number 47.

Build numbers from a few parts: Base 10 & the myriad system (万)

Master the logical architecture of Japanese numbers: combine ten basic digits to reach 99, handle irregular phonetics in hundreds and thousands, and master the 4-digit myriad shift at 10,000 (万).

Positional Number System: Building Tens, Hundreds & Thousands

multiplier digit

base unit: tens

ones place

copula

sanjuugo desu

It is 35 (literally: three-tens five).

Tens Construction (Multiplier + 十) vs Teens (十 + Digit)

Micro-Shift

全部で三十あります。

Multiplying tens: Digit precedes 十 (さん + じゅう = 30)There are thirty in all.

To say 30, place the multiplier before 10: 三 + 十 (さんじゅう).

Mental Model: The Transparent Lego System (Base 10)

Unlike European languages with historical oddities like “eleven,” “twelve,” or French “quatre-vingts” (four-twenties), Japanese numbers are built from pure mathematical Lego blocks:

1 to 10: 一(いち), 二(に), 三(さん), 四(よん / し), 五(ご), 六(ろく), 七(なな / しち), 八(はち), 九(きゅう / く), 十(じゅう).
11 is simply 10 + 1: 十一(じゅういち).
20 is 2 × 10: 二十(にじゅう).
99 is (9 × 10) + 9: 九十九(きゅうじゅうきゅう).

The Critical Threshold: The 4-Digit Myriad System (万)

The single biggest stumbling block for English speakers is large numbers:

Western Counting Groups by 1,000s (3 Zeros): Thousand (1,000) → Million (1,000,000) → Billion (1,000,000,000).
Japanese Counts Strictly by 10,000s (4 Zeros / 万(まん)):
10,000 is not ten-thousand; it has its own base unit: 一万(いちまん).
100,000 is 10 ten-thousands: 十万(じゅうまん).
1,000,000 is 100 ten-thousands: 百万(ひゃくまん).
10,000,000 is 1,000 ten-thousands: 千万(いっせんまん).
100,000,000 introduces the next 4-zero threshold: 一億(いちおく) (10,000 × 10,000).

The Irregular Phonetic Shifts in Hundreds and Thousands

When counting hundreds (百(ひゃく)) and thousands (千(せん)), several numbers cause phonetic sound mutations (gemination or voicing):

Hundreds (百(ひゃく)): 100 is bare 百(ひゃく) (no いち) · 300 is 三百(さんびゃく) (byaku) · 600 is 六百(ろっぴゃく) (pyaku) · 800 is 八百(はっぴゃく) (pyaku).
Thousands (千(せん)): 1,000 is bare 千(せん) (no いち) · 3,000 is 三千(さんぜん) (zen) · 8,000 is 八千(はっせん) (pause + sen).

Currency and Numbers in Daily Life

Conversation

In Dialogue

Sensei
教科書の四十五(よんじゅうご)ページを開いてください。
Please open page 45 of your textbook.
Student
はい、開きました！どの問題を読みますか？
Yes, opened! Which problem should we read?

Tips and Common Traps

Hana· Key point
Two counting lineages: Japanese uses Sino-Japanese numbers (一, 二, 三...) for arithmetic, clock hours, and measurements, and native Japanese words (ひとつ, ふたつ, みっつ...) for general physical items up to ten.
Maru· Common trap
Unlucky homophones: 四 can be read し (shi) or よん (yon). Because し sounds identical to 死 (death), よん is preferred in daily life! Similarly, 九 is often read きゅう (kyuu) to avoid sounding like 苦 (ku = suffering)!

Quick Check

47は日本語(にほんご)で「___」と読(よ)みます。47 is read as ‘...’ in Japanese.

Select the standard everyday reading for the number 47.