Meaning
The kanji 倍 clearly conveys the concepts of "double," "twice," or "multiply." It also acts as a suffix, meaning "-fold" or "times." This character primarily describes an increase in quantity, magnitude, or intensity by a specific factor. As such, it's fundamental for numerical comparisons and expressing growth in Japanese.
Its visual structure provides insight into its meaning. The left side, 人, is the "person" radical. This component, pronounced ninben when on the left, is a compressed form of 人 (person) and often suggests human action, number, or relation. The right component, 咅, serves as a crucial phonetic element, though it's not commonly used as a standalone kanji in modern Japanese. Historically, 咅 depicted two mouths (口) stacked or juxtaposed, symbolizing "repetition," "stacking," or "more." This visual concept naturally led to the idea of multiplication or doubling. When 人 (person) and 咅 (repetition/stacking) combine, they conceptually form the idea of a person repeating or multiplying something. This results in a larger quantity or effect, hence the meanings "double" or "multiply."
Understanding this etymology helps learners appreciate how the kanji's form directly relates to its abstract meaning of increasing by a factor. The kanji 倍 has 10 strokes. It's part of the Joyo Kanji list, typically introduced in the 5th grade of elementary school in Japan, making it a foundational character for numerical increase and comparison. For JLPT, it's considered an N3 level kanji, highlighting its importance for intermediate learners.
Readings
On'yomi (音読み) — Chinese-derived readings
The primary, and almost exclusive, On'yomi reading for 倍 is バイ (BAI). You'll consistently find this reading in compound words, where it signals multiplication, doubling, or an increased factor. It's a versatile character, appearing as both a prefix and a suffix in mathematical and quantitative expressions.
倍数 (baisuu) — This compound refers to a "multiple" in mathematics. For example, 6 is a multiple of 3 (３の倍数).
二倍 (nibai) — Meaning "double" or "twice." This is a very common expression for multiplying by two, such as 二倍の量 (nibai no ryō - double the amount).
倍率 (bairitsu) — This term denotes "magnification" or "ratio," often used in photography, microscopy, or even in describing the competitiveness of a test (e.g., 入学試験の倍率).
倍増 (baizou) — Refers to "doubling" or "increasing twofold." It implies a significant and direct increase, such as 売上の倍増 (uriage no baizou - doubling of sales).
数倍 (suubai) — Means "several times" or "many times," indicating an unspecified but significant multiplication, as in 数倍の速さ (suubai no hayasa - several times the speed).
Kun'yomi (訓読み) — Native Japanese readings
Unlike many other kanji, 倍 lacks any commonly used native Japanese Kun'yomi readings when it appears alone as a verb or adjective. Its primary role is within On'yomi compounds, where it conveys its core meaning of multiplication or doubling. This means you won't typically see 倍 used independently with a hiragana ending to form a native Japanese word. As a result, its reading is quite straightforward: just remember the On'yomi バイ for most practical uses.
Common Words & Compounds
倍 appears in many essential compounds, particularly when discussing numbers, ratios, and increases. Below are some of the most common and useful examples, categorized for easier understanding:
Numerical & Quantitative Expressions
二倍 (nibai) — double; twice. This is one of the most fundamental uses, indicating multiplication by two. For instance, 値段が二倍になる means "the price doubles."
三倍 (sanbai) — triple; three times. Similar to 二倍, but for a factor of three.
数倍 (suubai) — several times; many times. Used when the exact multiplier is not specified but is understood to be more than just double.
何倍 (nanbai) — how many times? This is an interrogative term used to ask about the multiplier. For example, 何倍の速さですか asks "how many times faster is it?"
倍数 (baisuu) — multiple (in mathematics). For example, 4, 6, and 8 are all multiples of 2.
Actions & Processes of Increase
倍増 (baizou) — doubling; increasing twofold. This compound implies an active process of making something double in quantity or size. For example, 売上が倍増する means "sales double."
倍加 (baika) — doubling; multiplying. Similar to 倍増, often used in a more formal or scientific context, such as 努力を倍加する (doryoku o baika suru - to redouble one's efforts).
Ratios & Rates
倍率 (bairitsu) — magnification; ratio. Commonly used for lenses (e.g., a telescope's magnification) or for the competition ratio of entrance exams (e.g., 入学試験の倍率 - entrance exam competition ratio).
等倍 (toubai) — same size; life-size; 1:1 ratio. This term indicates no magnification or reduction, often used in photography or printing.
Figurative & Abstract Uses
百倍 (hyakubai) — one hundred times; manifold. Used to express a very large or significant increase, often figuratively. For example, 百倍の努力 means "a hundred times the effort."
倍返し (baigaeshi) — paying back double. This phrase, popularized by a Japanese drama, implies returning a favor or, more often, a wrongdoing, with double the intensity.
Example Sentences
今年の売上は昨年の二倍になりました。
Kotoshi no uriage wa sakunen no nibai ni narimashita.
This year's sales doubled compared to last year's.
このレンズは五倍に拡大できます。
Kono renzu wa gobai ni kakudai dekimasu.
This lens can magnify five times.
明日から倍の努力をします。
Ashita kara bai no doryoku o shimasu.
I will put in double the effort starting tomorrow.
この資料を二倍に拡大してコピーしてください。
Kono shiryō o nibai ni kakudai shite kopī shite kudasai.
Please enlarge this document two times and copy it.
その象は猫の何十倍も大きいです。
Sono zō wa neko no nanjūbai mo ookii desu.
That elephant is tens of times larger than a cat.
人気の商品は定価の三倍で売られています。
Ninki no shōhin wa teika no sanbai de urareteimasu.
Popular products are being sold at triple their list price.
景気が回復し、雇用が倍増しました。
Keiki ga kaifuku shi, koyō ga baizou shimashita.
The economy recovered, and employment doubled.
あの店は以前より数倍広くなりました。
Ano mise wa izen yori suubai hiroku narimashita.
That shop became several times larger than before.
この薬は通常の二倍の効果があるそうです。
Kono kusuri wa tsūjō no nibai no kōka ga aru sō desu.
This medicine is said to be twice as effective as normal.
Memory Tip
To easily remember 倍, focus on its two main components. The left side is 人, the "person" radical, vividly depicting a human figure. On the right, you'll find 咅, a phonetic component crucial to the meaning, even though it doesn't stand alone. Visually, picture 咅 as two 口 (mouths) stacked on top of each other, or perhaps on a stand. This image of stacking or repetition can symbolize saying something twice, or repeating an action, leading to an increase. Imagine a person (人) actively making something repeat or stack up (咅) to create a double or multiplied amount. Another way to visualize it is a person holding up two identical items, effectively "doubling" their count or quantity. This mental image connects the visual components directly to the abstract meaning of "double" or "multiply," making the kanji much easier to recall.