Meaning
The kanji 億 (oku) represents the significant numerical value of one hundred million (100,000,000). It is a fundamental unit in the Japanese counting system for large numbers. You'll find it particularly crucial in financial contexts, population statistics, and discussions of vast scales, such as astronomical distances or geological timeframes. Grasping the meaning of 億 is essential for understanding Japanese news, economic reports, and scientific information.
Etymologically, 億 is a 形声字 (keisei-moji, phono-semantic character). It combines a semantic radical with a phonetic component. The left side, 人 (hito, person), acts as the radical. It hints at the original concept of "many people" or "a great multitude." This suggests the character's ancient usage might have been associated with a vast number of individuals. The right side is 意 (i), meaning "intention," "idea," or "thought." Interestingly, 意 itself is a compound of 音 (oto, sound) and 心 (kokoro, heart/mind). While 意 provides the phonetic clue, the combination of 人 and 意 together evolved to specifically denote this immense quantity: one hundred million.
Visually, 億 can be seen as a person (人) standing beside a complex idea (意). This emphasizes the sheer scale, which requires careful thought to grasp. It implies a number so large it's beyond simple enumeration, thus requiring a specific, standardized term. Today, its meaning is firmly fixed at 108, or one hundred million.
The kanji 億 has 15 strokes and is a Jōyō Kanji (常用漢字). This means it is among the 2,136 characters designated for common use in Japan. While not assigned to a specific elementary school grade, students typically learn it in secondary education. This reflects its importance for advanced vocabulary and comprehension.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi for 億 is オク (OKU). This reading is exclusively used to express the numerical value of one hundred million. It plays a critically important role in many aspects of Japanese life, from economic data to historical timelines.
一億 (ichioku) — one hundred million. This is the most basic usage. You'll often see it when referring to the population of Japan or large monetary figures.
数億 (sūoku) — several hundred million. This term expresses an unspecified large quantity, specifically in the range of hundreds of millions. For example, you might hear it when discussing investment amounts or the number of views on a viral video.
億万長者 (okumanchōja) — billionaire, multi-millionaire. This common term refers to extremely wealthy individuals. Literally, it means "hundred million ten thousand rich person," signifying immense wealth.
The on'yomi reading オク is always pronounced with a clear 'o' sound followed by 'ku', and it remains consistent regardless of context. It forms the backbone of how numerical values in the hundreds of millions are articulated in Japanese. You'll often find it appearing in conjunction with other numerical units like 万 (man, ten thousand) and 兆 (chō, trillion) to form even larger numbers.
Kun'yomi (訓読み) — Native Japanese readings
The kanji 億 does not have any native Japanese kun'yomi readings. Since 億 represents a highly specific, large numerical concept borrowed from Chinese, it has retained only its on'yomi, オク. Many kanji for large numbers or abstract scientific terms often lack kun'yomi. This is because their concepts were introduced to Japan along with their Chinese readings. This makes 億 relatively straightforward in terms of readings. Learners only need to memorize one reading, オク, and consistently associate it with the value of one hundred million.
Common Words & Compounds
The kanji 億 is predominantly used in numerical contexts, particularly for expressing large quantities across various fields. Here are some common words and compounds, categorized for clarity:
Numerical Expressions
一億 (ichioku) — One hundred million. Often used for population figures or large sums of money.
百億 (hyakuoku) — Ten billion (literally "one hundred hundred-million"). In the Japanese counting system, values increase by factors of 10,000, not 1,000. So, 100 x 100,000,000 = 10,000,000,000.
千億 (sen'oku) — One hundred billion (literally "one thousand hundred-million").
数億 (sūoku) — Several hundred million. This term is used when the exact number isn't specified but falls within this magnitude.
何億 (nan'oku) — How many hundred million? You'll use this in questions about large quantities.
数十億 (sūjūoku) — Several billion (literally "several tens of hundred-million").
Financial and Scale-related Terms
億単位 (okutan'i) — In units of hundreds of millions. This describes something measured or expressed in increments of 100,000,000.
億万長者 (okumanchōja) — Billionaire, multimillionaire. This term refers to a person of immense wealth.
億万 (okuman) — Immense number, a myriad. This term is often used metaphorically to express an incredibly vast quantity, one beyond easy counting. It can also be taken literally as "hundred million ten thousand."
億兆 (okuchō) — Hundreds of millions and trillions. This term signifies an extremely large or immeasurable quantity, combining 億 (hundred million) and 兆 (trillion).
億年 (okunen) — Hundred million years. You'll frequently encounter this term in geology, astronomy, and paleontology to describe vast periods of time.
億越え (okugoe) — Exceeding a hundred million. This is often used in reports on sales figures or milestones.
These compounds demonstrate the versatility of 億 in creating precise and powerful expressions of scale and magnitude. They appear in various contexts, from personal finances to universal timescales.
Example Sentences
日本の人口は約一億です。
Nihon no jinkō wa yaku ichioku desu.
Japan's population is approximately one hundred million.
この映画は制作費に数億ドルかかりました。
Kono eiga wa seisakuhi ni sūoku doru kakarimashita.
This movie cost several hundred million dollars to produce.
地球が誕生したのは数十億年も前です。
Chikyū ga tanjō shita no wa sūjūokunen mo mae desu.
The Earth was formed several billion years ago.
彼は宝くじで一億を当てた億万長者になりました。
Kare wa takarakuji de ichioku wo ateta okumanchōja ni narimashita.
He became a multi-millionaire after winning one hundred million yen in the lottery.
その会社は今年、売上が百億を超えました。
Sono kaisha wa kotoshi, uriage ga hyakuoku wo koemashita.
That company's sales exceeded ten billion yen this year.
政府は総額数億の支援金を発表しました。
Seifu wa sōgaku sūoku no shienkin wo happyō shimashita.
The government announced several hundred million in total aid money.
宇宙には何千億という星があると言われています。
Uchū ni wa nanzen'oku to iu hoshi ga aru to iwareteimasu.
It is said that there are hundreds of billions of stars in the universe.
このプロジェクトの予算は億単位で見積もられています
Kono purojekuto no yosan wa okutan'i de mitsumorareteimasu.
The budget for this project is estimated in units of hundreds of millions.
彼は億万の富を築き、慈善事業に貢献しました。
Kare wa okuman no tomi wo kizuki, jizenjigyō ni kōken shimashita.
He amassed immense wealth and contributed to charitable endeavors.
Memory Tip
To remember 億, break it down into its components: the radical 人 (ninben, person) on the left, and 意 (i, intention/idea) on the right. Visualize a single person (人) standing before an enormous task or grappling with a profound idea (意) of counting one hundred million things. This sheer number is so vast that it requires significant "intention" or mental effort just to conceive of it. Alternatively, imagine one hundred million people (人) who collectively share a single thought or intention (意). This combination—a single individual grasping a huge concept, or a multitude of people united in thought—visually reinforces the idea of an immense, almost overwhelming quantity like a hundred million.