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B2 noun #4,000 most common 10 min read

指数

shisuu Top 4,000

Practice it Examples Notes & Tips 指数 in 30 Seconds

Explanation 指数 in your Level:

At the A1 level, you don't need to use the word '指数' (shisū) yourself, but you might see it on a weather app. Think of it as a special 'number' that tells you something useful. For example, a 'UV index' tells you if you need a hat. It's like a grade from 1 to 100. If the number is high, the thing it's measuring is strong or high. You can just remember it means 'a score' or 'a level' for now. Don't worry about the math part yet. Just look at the word as a way for news people to show information simply using numbers. For example, 'Sentaku Shisū' means 'Laundry Number'—a high number means it's a good day to wash clothes!

At the A2 level, you will start to recognize '指数' (shisū) in compound words. You might hear it in the weather report or simple health news. It means 'index' or 'scale.' It is a noun. You can think of it as a number that helps compare things. For example, 'Bukka Shisū' is the 'Price Index.' If prices go up, this number goes up. You will often see it followed by 'ga agaru' (goes up) or 'ga sagaru' (goes down). It is a formal word, so you won't use it with friends, but you will see it in newspapers. Just remember that it is a 'pointing number' that shows a trend or a level.

At the B1 level, you should understand that '指数' (shisū) is used for statistical measurements. You will encounter it in business news and social studies. It is often used to describe how much something has changed compared to a 'base year' (usually set at 100). You should be able to understand phrases like 'Nikkei Average Index' or 'Consumer Price Index.' You also start to see its mathematical meaning: 'exponent' or 'power.' For example, in 10 to the power of 2, the 2 is the 'shisū.' At this level, you should be able to use it in a sentence to describe a trend, like 'The index showed a slight increase.'

At the B2 level, you are expected to use '指数' (shisū) accurately in professional or academic contexts. You should distinguish it from 'shihyō' (indicator). An index is a specific calculated value, while an indicator is a broader sign. You should be familiar with 'exponential growth' (shisū kansū-teki na seichō) and be able to discuss economic trends using this vocabulary. You can use it in compound words like 'intelligence quotient' (chinō shisū) or 'discomfort index' (fukai shisū). You should also understand how to use verbs like 'sanshutsu suru' (calculate) with 'shisū.' Your usage should reflect an understanding of data and comparison.

At the C1 level, you should have a nuanced command of '指数' (shisū). You can use it to discuss complex econometric models, mathematical proofs involving exponents, and social science research. You understand the difference between a simple index and a weighted index. You can fluently discuss the 'shisū hōsoku' (laws of exponents) and use the term 'shisū-ka suru' (to index something) to describe the process of turning raw data into a comparable scale. You are also aware of the word's presence in high-level literature and technical manuals, where it might describe logarithmic scales or advanced statistical benchmarks. Your speech sounds precise and authoritative.

At the C2 level, '指数' (shisū) is a tool you use with absolute precision. You can critique the methodology of how a specific 'shisū' was calculated, discussing potential biases in the base year or the selection of variables. You can navigate highly technical discussions in fields like quantitative finance, theoretical physics, or advanced data science where 'shisū' refers to complex power functions and multi-variable indices. You can use the term metaphorically in sophisticated writing to describe rapid, non-linear changes in society or technology. You are fully comfortable with all its mathematical, economic, and lifestyle applications, switching between them seamlessly based on the context.

Practice it Examples Notes & Tips

指数 in 30 Seconds

Shisū is a noun meaning 'index' or 'exponent,' used to measure statistical changes or mathematical powers.
Commonly found in stock market reports (Nikkei Index) and weather forecasts (UV Index, Discomfort Index).
In math, it refers to the exponent in powers like x³, where 3 is the shisū.
It differs from 'shihyō' (indicator) by being a specific, calculated numerical formula rather than a general sign.

The Japanese word 指数 (しすう - shisū) is a versatile term primarily used in two major domains: mathematics and economics/statistics. At its core, it represents a numerical value that serves as a benchmark or a power. In a mathematical context, it refers to an 'exponent' or 'power'—the small number placed above and to the right of a base number to indicate how many times the base is multiplied by itself. In economics and social sciences, it translates to an 'index' or 'indicator,' representing a statistical measure of changes in a representative group of individual data points. Understanding shisū is crucial for anyone navigating professional Japanese environments, as it appears in daily news reports regarding the stock market, weather forecasts, and academic research.

Economic Context: In economics, 指数 is used to track trends over time. For example, the Consumer Price Index (CPI) is known as 消費者物価指数 (shōbishsha bukka shisū). It provides a snapshot of how prices for goods and services have changed relative to a base year, usually set at 100. When you hear that an index has 'risen to 105,' it means there has been a 5% increase from the reference point.

日経平均指数が過去最高値を更新しました。(The Nikkei Stock Average index has reached a new record high.)

Mathematical Context: In algebra, 指数 refers to the exponent. For instance, in the expression 10³, the number 3 is the 指数. This leads to the term 指数関数 (shisū kansū), meaning 'exponential function,' which is a common concept in both pure math and descriptions of rapid growth (exponential growth).

この計算では、指数法則を適用する必要があります。(In this calculation, it is necessary to apply the laws of exponents.)

Beyond these formal uses, shisū appears in lifestyle contexts, such as the 不快指数 (fukai shisū) or 'discomfort index,' which measures how uncomfortable the weather feels based on temperature and humidity. Similarly, the 紫外線指数 (shigaisen shisū) or 'UV index' helps people decide whether to wear sunscreen. These everyday applications make the word highly relevant for daily life in Japan, especially during the humid summer months.

今日の不快指数は非常に高いので、熱中症に注意してください。(The discomfort index is very high today, so please be careful of heatstroke.)

Cultural Nuance: In Japan, precision is highly valued in public reporting. Therefore, shisū is preferred over more vague terms like 'trend' or 'level' when hard data is being discussed. Using shisū signals that the speaker is relying on standardized metrics rather than subjective observation.

幸福指数の調査で、この国は上位にランクインした。(This country ranked high in the happiness index survey.)

物価指数の変動を注視しています。(We are closely monitoring the fluctuations in the price index.)

In summary, whether you are analyzing a graph in a boardroom, solving an equation in a classroom, or checking the weather on your phone, shisū is the essential term for quantifying relative change and mathematical magnitude. It bridges the gap between abstract calculation and real-world measurement.

Using 指数 (shisū) correctly requires understanding its grammatical placement as a noun that often forms compound words. In Japanese, shisū frequently acts as a suffix to define specific metrics. For example, by adding it to 'price' (物価) or 'intelligence' (知能), you create 'price index' (物価指数) and 'intelligence quotient' (知能指数 - IQ). This section will explore the structural patterns and common verb pairings associated with this word.

Compound Noun Structure: The most common way to use shisū is to attach it directly after another noun. The pattern is: [Topic/Category] + 指数. Examples: 普及指数 (fukyuu shisū - diffusion index), 景気動向指数 (keiki dōkō shisū - business condition index).

最新の消費者物価指数が発表された。(The latest consumer price index was announced.)

Verbs of Change: Since an index measures change, it is often used with verbs like 上昇する (jōshō suru - to rise), 低下する (teika suru - to fall), or 推移する (suii suru - to transition/fluctuate). Example: 指数が上昇傾向にある (The index is on an upward trend).

生産性指数が前年同期比で低下した。(The productivity index fell compared to the same period last year.)

この変数を指数関数的に増加させる。(Make this variable increase exponentially.)

Another frequent construction involves 'calculating' or 'setting' the index. Verbs like 算出する (sanshutsu suru - to calculate/compute) or 設定する (settei suru - to set) are standard. In business reports, you might see: 指数を算出した結果... (As a result of calculating the index...).

独自のアルゴリズムで市場の信頼度を指数化した。(We indexed market confidence using a unique algorithm.)

Comparison Patterns: To compare indices, use 比較する (hikaku suru) or 上回る (uwamawaru - to exceed). For example: A指数がB指数を大幅に上回った (Index A significantly exceeded Index B).

各国の教育水準を同じ指数で比較するのは難しい。(It is difficult to compare the educational standards of various countries using the same index.)

コンピュータの処理能力は指数関数的に向上している。(Computer processing power is improving exponentially.)

Whether used in formal economics or abstract math, shisū typically functions as a precise, objective noun. It is rarely used in casual conversation unless referring to common public metrics like the UV index or the discomfort index.

If you spend any time watching Japanese television or reading news sites, you will encounter 指数 (shisū) daily. Its presence is ubiquitous in professional and informational media. This section details the specific environments where you are most likely to hear this term and the context it carries in those settings.

The Evening News (Economy Segment): Every weekday evening, news anchors report on the 日経平均株価 (Nikkei Stock Average). They often follow this with other indices like the 東証株価指数 (TOPIX). You will hear phrases like '指数は続伸しました' (The index continued to rise) or '主要な指数が軒並み下落しました' (Major indices fell across the board).

今日の東京株式市場では、主要な指数が反発しました。(In today's Tokyo stock market, major indices rebounded.)

Weather Forecasts (Lifestyle Indices): Japanese weather segments are famous for their 'lifestyle indices.' They don't just tell you the temperature; they give you the 洗濯指数 (laundry index—how quickly clothes will dry), the 不快指数 (discomfort index), and the ビール指数 (beer index—how much people will want to drink beer based on the heat). These are all playful but informative uses of shisū.

明日の洗濯指数は「100」で、外干しに最適です。(Tomorrow's laundry index is 100, perfect for hanging clothes outside.)

数学の授業で指数の計算を習いました。(I learned how to calculate exponents in math class.)

In corporate environments, shisū is used during performance reviews and strategic planning. Managers might discuss the 生産性指数 (productivity index) or 従業員満足度指数 (employee satisfaction index). It implies a data-driven approach to management.

我が社の顧客満足度指数は、業界平均を上回っています。(Our company's customer satisfaction index is above the industry average.)

Academic and Scientific Research: Research papers use shisū to quantify phenomena. For example, the BMI (体格指数) is used in health sciences, and the ジニ係数 (Gini coefficient) is often referred to in the context of income inequality indices.

この論文は、経済格差を示す様々な指数を分析している。(This paper analyzes various indices that show economic disparity.)

感染者数が指数関数的に増加するリスクがある。(There is a risk that the number of infected people will increase exponentially.)

In summary, shisū is a fundamental word for anyone who wants to understand Japanese data, science, or finance. It is the language of measurement and comparison in the modern Japanese-speaking world.

While 指数 (shisū) is a straightforward technical term, learners often confuse it with other similar-sounding or conceptually related words. Understanding these distinctions is key to achieving B2 level fluency and beyond. This section highlights the most common pitfalls and how to avoid them.

Confusion with 指標 (shihyō): This is the most frequent mistake. 指標 (shihyō) means 'indicator' or 'target.' While an index (shisū) is always a numerical value based on a formula, an indicator (shihyō) can be more qualitative or represent a goal. For example, 'GDP growth' is an indicator, but the 'Consumer Price Index' is specifically a shisū.

誤: 成功の指数を立てる。
正: 成功の指標を立てる。(Set an indicator/benchmark for success.)

Confusion with 数値 (sūchi): 数値 (sūchi) simply means 'numerical value' or 'data point.' Shisū is a specific type of numerical value that shows a ratio or power. You wouldn't call your height a shisū; it's a sūchi. However, your BMI is a shisū because it's a calculated ratio.

誤: 体温の指数を測る。
正: 体温の数値を確認する。(Check the numerical value of the body temperature.)

誤: 彼は高い知能数を持っている。
正: 彼は高い知能指数を持っている。(He has a high IQ.)

Another error involves the mathematical use. Learners sometimes use shisū when they actually mean 係数 (keisū), which is a 'coefficient' (the number multiplied by a variable, like the 5 in 5x). An exponent (shisū) is the power (the 3 in x³).

xの2乗の「2」は指数であり、係数ではありません。(The '2' in x squared is an exponent, not a coefficient.)

Misusing 'Exponentially': In English, people often say 'exponentially' to mean 'a lot' or 'very fast.' In Japanese, 指数関数的 (shisū kansū-teki) is more strictly mathematical. While it is used for rapid growth, using it for simple linear growth is considered imprecise in professional contexts.

売り上げが指数関数的に伸びている。(Sales are growing exponentially—implies a doubling or tripling effect, not just a steady rise.)

物価指数を計算する際は、基準年を確認してください。(When calculating the price index, please check the base year.)

By keeping these distinctions in mind—index vs. indicator, index vs. value, and exponent vs. coefficient—you will use shisū with the precision expected of a high-level Japanese speaker.

To truly master 指数 (shisū), it helps to compare it with other terms that deal with numbers, measurements, and trends. Japanese has a rich vocabulary for data, and choosing the right word depends on the specific nuance you want to convey. Here is a breakdown of similar words and how they differ from shisū.

指標 (Shihyō) - Indicator / Benchmark: While shisū is a specific numerical formula (like the Nikkei 225), shihyō is a broader term for any standard used to judge or measure something. Shihyō can include non-numerical targets.
Usage: 'Customer satisfaction is a key indicator (shihyō) of our success.'

経済指標を分析して、将来を予測する。(Analyze economic indicators to predict the future.)

係数 (Keisū) - Coefficient: Used primarily in mathematics and physics, a coefficient is a constant value that multiplies a variable. Unlike shisū (which is a power), keisū stays on the same line as the variable.
Usage: 'The expansion coefficient (bōchō keisū) of this metal is high.'

この数式では、摩擦係数を無視できる。(In this formula, the friction coefficient can be ignored.)

エンゲル係数が上昇し、生活が苦しくなっている。(The Engel coefficient is rising, and life is becoming harder.)

比率 (Hiritsu) - Ratio / Percentage: Hiritsu is a simple comparison between two quantities (e.g., 2:1 or 50%). Shisū is usually a more complex calculation that tracks these ratios over time against a fixed base point.
Usage: 'The ratio (hiritsu) of men to women in the office is equal.'

男女の賃金比率を調査する。(Investigate the wage ratio between men and women.)

Other alternatives include 尺度 (shakudo) which means 'scale' or 'measure' (often used for psychological scales), and 基準 (kijun) which means 'standard' or 'criterion.' While shisū provides the data, kijun provides the rule for what that data means.

評価の基準を明確にする必要がある。(It is necessary to clarify the criteria for evaluation.)

心理学的な尺度を用いてストレスを測定する。(Measure stress using a psychological scale.)

By mastering these synonyms, you can express yourself with greater nuance and precision, ensuring that your Japanese sounds professional and contextually appropriate.

How Formal Is It?

Fun Fact

The term was popularized in the Meiji era when Western mathematical and economic concepts were being translated into Japanese. The translators chose 'pointing number' to capture the essence of an 'indicator.'

Pronunciation Guide

UK ʃisɯː

US ʃisɯː

The pitch accent is 'Heiban' (Flat), meaning the pitch starts low and stays high.

Rhymes With

kisu (kiss) risu (squirrel) misu (mistake) jisu (JIS standards) gisu (gear) hisu (hysteria) isu (chair) kisu (sand borer fish)

Common Errors

Pronouncing 'shisū' as 'shisu' (short 'u'). The long 'u' is vital.
Confusing it with 'shishū' (embroidery).
Confusing it with 'shishu' (defending to the death).
Confusing it with 'shisō' (thought/ideology).
Over-stressing the first syllable.

Difficulty Rating

Reading 4/5

The kanji are common but the context is often technical, requiring B2 level reading skills.

Writing 4/5

Writing '指数' correctly requires knowing the 'finger' and 'number' kanji, which are mid-level.

Speaking 3/5

Pronunciation is easy, but using it correctly in context requires practice.

Listening 3/5

Easily recognizable in news and weather reports once learned.

What to Learn Next

Prerequisites

数 (Number) 指す (To point) 計算 (Calculation) 統計 (Statistics) 物価 (Prices)

Learn Next

指標 (Indicator) 相関 (Correlation) 偏差値 (Standard deviation score) 係数 (Coefficient) 対数 (Logarithm)

Advanced

回帰分析 (Regression analysis) 時系列データ (Time-series data) 加重平均 (Weighted average) デフレ (Deflation) インフレ (Inflation)

Grammar to Know

Compound Nouns (熟語)

物価 + 指数 = 物価指数 (Noun + Noun)

Adverbial form of ~teki (〜的に)

指数関数的 + に = 指数関数的に (Exponentially)

Passive Voice in formal reporting

指数が算出される (The index is calculated)

Transitive vs Intransitive

指数を上げる (Raise the index) vs 指数が上がる (Index rises)

Comparison using 'to' or 'yori'

去年の指数と比較する (Compare with last year's index)

Examples by Level

今日の不快指数は高いです。

Today's discomfort index is high.

Simple noun usage with 'desu'.

洗濯指数をチェックします。

I will check the laundry index.

Object marker 'o' used with 'check suru'.

UV指数は5です。

The UV index is 5.

Stating a specific value.

この指数は何ですか？

What is this index?

Using 'nani' to ask for a definition.

指数が上がりました。

The index went up.

Subject marker 'ga' with an intransitive verb.

指数を見ます。

I look at the index.

Basic verb 'miru' (to see/look).

あつい指数ですね。

It's a 'hot' index, isn't it?

Adding 'ne' for agreement (informal/natural).

この数字は指数です。

This number is an index.

Defining a number as a specific term.

物価指数が少し上がりました。

The price index rose a little.

Compound noun 'bukka shisū'.

知能指数を測るテストを受けました。

I took a test to measure my IQ.

Compound noun 'chinō shisū' (IQ).

日経平均指数はいくらですか？

What is the Nikkei Average Index?

Asking for a specific quantity using 'ikura'.

明日の指数は低いです。

Tomorrow's index is low.

Adjective 'hikui' (low) describing the noun.

ニュースで指数を聞きました。

I heard the index on the news.

Particle 'de' indicating the location/source.

このグラフは指数を示しています。

This graph shows the index.

Verb 'shimesu' (to show/indicate).

不快指数が80を超えました。

The discomfort index exceeded 80.

Verb 'koeru' (to exceed).

指数の意味がわかりません。

I don't understand the meaning of 'index'.

Genitive particle 'no' connecting two nouns.

消費者物価指数は経済の健康状態を表します。

The Consumer Price Index represents the health of the economy.

Verb 'arawasu' (to represent/express).

数学で指数の計算を習いました。

I learned the calculation of exponents in math.

Focusing on the mathematical meaning.

この指数は前月と比較されています。

This index is being compared with the previous month.

Passive form 'hikaku sarete iru'.

不快指数が高いと、イライラしやすくなります。

When the discomfort index is high, it's easy to get frustrated.

Conditional 'to' indicating a natural consequence.

指数の変動をグラフにまとめました。

I summarized the fluctuations of the index in a graph.

Noun 'hendō' (fluctuation).

株価指数が急落して、投資家が驚いた。

The stock index plummeted, and investors were surprised.

Verb 'kyūraku suru' (to plummet).

彼は指数の法則を完璧に理解している。

He perfectly understands the laws of exponents.

Term 'shisū no hōsoku'.

基準年を100として指数を算出します。

The index is calculated with the base year as 100.

Using '...to shite' (as ...).

景気動向指数は、今後の経済予測に不可欠です。

The business condition index is essential for future economic forecasting.

Adjective 'fukasetsu' (essential).

コンピュータの性能は指数関数的に向上している。

Computer performance is improving exponentially.

Adverbial phrase 'shisū kansū-teki ni'.

各国の幸福指数を比較する調査が行われた。

A survey was conducted comparing the happiness indices of various countries.

Compound 'kōfuku shisū'.

その数式における指数の役割を説明してください。

Please explain the role of the exponent in that formula.

Noun 'yakuwari' (role).

物価指数が上昇傾向にあり、懸念が広がっている。

The price index is on an upward trend, and concerns are spreading.

Noun 'jōshō keikō' (upward trend).

独自の指数を用いて、企業の社会的責任を評価する。

Evaluate corporate social responsibility using a unique index.

Using 'mochiite' (using/by means of).

指数の算出方法に誤りがあったことが判明した。

It was revealed that there was an error in the calculation method of the index.

Noun 'sanshutsu hōhō' (calculation method).

この指数は季節調整が行われています。

This index is seasonally adjusted.

Technical term 'kisetu chōsei' (seasonal adjustment).

ジニ係数などの格差指数は、社会の安定性を測る重要な尺度だ。

Inequality indices such as the Gini coefficient are important measures of social stability.

Combining 'shisū' with 'shakudo' (scale).

指数平滑法を用いて将来の需要を予測する。

Predict future demand using the exponential smoothing method.

Technical term 'shisū heikatsu-hō'.

市場のボラティリティを示す指数が急上昇した。

The index indicating market volatility surged.

Relative clause 'volatility o shimesu'.

このモデルは、指数の重み付けを再考する必要がある。

This model needs to reconsider the weighting of the indices.

Noun 'omomizuke' (weighting).

人口減少の影響は指数関数的に拡大する恐れがある。

There is a fear that the impact of population decline will expand exponentially.

Using 'osore ga aru' (there is a fear/risk).

経済指標と指数の相関関係を詳細に分析した。

We detailedly analyzed the correlation between economic indicators and indices.

Noun 'sōkan kankei' (correlation).

その指数は、複数のマクロ経済変数を統合したものである。

That index is an integration of multiple macroeconomic variables.

Noun 'tōgō' (integration).

指数の基準改定により、過去のデータとの連続性が失われた。

Due to the revision of the index base, continuity with past data was lost.

Noun 'kijun kaitei' (base revision).

指数型分布の特性を考慮した確率モデルを構築する。

Construct a stochastic model considering the characteristics of exponential distribution.

Technical term 'shisū-gata bunpu'.

当該指数は、実体経済の乖離を如実に物語っている。

The index in question vividly illustrates the divergence from the real economy.

Advanced idiom 'nyojitsu ni monogatatte iru'.

指数の収束性を証明するために、高度な微積分を用いる。

Use advanced calculus to prove the convergence of the index.

Technical term 'shūsoku-sei' (convergence).

複雑系における指数の振る舞いは、しばしば予測を裏切る。

The behavior of indices in complex systems often defies prediction.

Advanced phrase 'yosoku o uragiru'.

指数の恣意的な操作は、市場の信頼を根本から揺るがす。

Arbitrary manipulation of indices fundamentally shakes market confidence.

Advanced noun 'shiiteki sōsa' (arbitrary manipulation).

指数の対数変換を行い、データの分散を安定させる。

Perform a logarithmic transformation of the index to stabilize data variance.

Technical term 'taisū henkan'.

グローバルな文脈において、開発指数の定義は常に議論の的となる。

In a global context, the definition of development indices is always a subject of debate.

Idiom 'giron no mato' (subject of debate).

指数の感度分析により、主要なリスク要因を特定した。

Identified major risk factors through sensitivity analysis of the index.

Technical term 'kando bunseki' (sensitivity analysis).

Synonyms

指標インデックス数値尺度計数

Antonyms

実数

Common Collocations

指数を算出する

指数が上昇する

指数関数的な

指数を改定する

指数に反映される

指数を比較する

主要な指数

指数を重み付ける

指数の法則

不快指数計

Common Phrases

日経平均株価指数

— The Nikkei 225 Stock Average Index, the most famous stock index in Japan.

日経平均株価指数が3万円を超えた。

消費者物価指数

— The Consumer Price Index (CPI), used to measure inflation.

消費者物価指数が前年を上回った。

知能指数

— Intelligence Quotient (IQ).

彼の知能指数は非常に高い。

不快指数

— Discomfort Index, measuring humidity and temperature effects on humans.

夏の京都は不快指数が高い。

紫外線指数

— UV Index, measuring the strength of ultraviolet radiation.

今日は紫外線指数が「極端に強い」です。

洗濯指数

— Laundry Index, indicating how well clothes will dry outdoors.

洗濯指数が良いので、シーツを洗おう。

景気動向指数

— Business Condition Index, used to judge the state of the economy.

景気動向指数が改善を示している。

指数関数的成長

— Exponential growth, used for things that increase very rapidly.

技術の進歩は指数関数的成長を続けている。

普及指数

— Diffusion Index (DI), often used in market research.

スマートフォンの普及指数を調査する。

体格指数

— Body Mass Index (BMI).

体格指数を計算して健康管理をする。

Often Confused With

指数 vs 指標 (Shihyō)

An indicator (shihyō) is a broader sign; an index (shisū) is a specific numerical formula.

指数 vs 係数 (Keisū)

A coefficient (keisū) multiplies a variable; an exponent (shisū) raises it to a power.

指数 vs 数値 (Sūchi)

A numerical value (sūchi) is any raw number; an index (shisū) is a calculated relative value.

Idioms & Expressions

"指数関数的に増える"

— To increase at a very fast, non-linear rate (like 2, 4, 8, 16...).

うわさが指数関数的に増えていった。

Neutral

"指数を弾き出す"

— To calculate or 'churn out' a specific index/numerical value.

コンピュータが最新の指数を弾き出した。

Informal/Journalistic

"指数を睨む"

— To watch the indices closely (often in stock trading).

投資家は常にアメリカの指数を睨んでいる。

Business

"指数と睨めっこする"

— To stare at indices for a long time (implies intensity or frustration).

一日中、株価指数と睨めっこしていた。

Casual

"指数が躍る"

— When indices fluctuate wildly or show exciting numbers.

新聞の一面に景気指数の数字が躍った。

Journalistic

"指数に一喜一憂する"

— To be alternately happy and sad depending on the index fluctuations.

毎日の株価指数に一喜一憂してはいけない。

Neutral

"指数の罠"

— The 'trap' of looking only at indices and missing the real situation.

統計指数の罠にはまらないよう注意が必要だ。

Academic/Critical

"指数が底を打つ"

— When an index hits its lowest point before starting to rise.

景気指数がついに底を打ったようだ。

Economic

"指数を牽引する"

— When a specific sector or stock pulls the whole index up.

ハイテク株が指数を牽引している。

Business

"指数の裏を読む"

— To look behind the numbers of an index to find the truth.

優秀なアナリストは指数の裏を読む。

Professional

Easily Confused

指数 vs 指数 (Shisū)

Both deal with numbers and tracking.

Shisū is a calculated ratio or a power; Shihyō is a general benchmark or target.

日経平均は指数(shisū)だが、GDPは経済指標(shihyō)だ。

指数 vs 係数 (Keisū)

Both are mathematical terms used in formulas.

Keisū is the number *before* the variable; Shisū is the number *above* it.

5x³において、5は係数、3は指数である。

指数 vs 比率 (Hiritsu)

Both show relationships between numbers.

Hiritsu is a simple ratio (A:B); Shisū is a ratio tracked against a base time/value.

男女比率は1:1だが、賃金指数は年々変化する。

指数 vs 偏差値 (Hensachi)

Both are standardized scores.

Hensachi is a standard score showing relative position in a group; Shisū shows change over time.

模試の偏差値は高いが、物価指数は関係ない。

指数 vs 定数 (Teisū)

Both are math nouns.

Teisū is a constant that doesn't change; Shisū is an exponent or a variable index.

円周率は定数だが、成長率は指数で表される。

Sentence Patterns

[Noun]指数が[Verb: Intransitive]

株価指数が上がった。

[Noun]指数を[Verb: Transitive]

不快指数を計算する。

指数関数的に[Verb/Adjective]

指数関数的に増加している。

指数に基づいた[Noun]

指数に基づいた投資判断。

指数の[Noun]改定

指数の基準改定を行う。

[Noun]指数は[Number]です

UV指数は8です。

[Noun]指数によると、...

物価指数によると、インフレが進んでいる。

指数の[Noun]特性を[Verb]

指数の収束特性を分析する。

Word Family

Nouns

指数 (Index/Exponent)

指数関数 (Exponential function)

指数部 (Exponent part in computing)

Verbs

指数化する (To index/standardize into an index)

指数的に増える (To increase exponentially)

Adjectives

指数関数的な (Exponential)

指標 (Indicator)

統計 (Statistics)

対数 (Logarithm)

係数 (Coefficient)

数値 (Numerical value)

How to Use It

frequency

Very high in media and professional life; moderate in casual daily life.

Common Mistakes

Using 'shisū' for a simple count of people. → 人数 (ninzū)
'Shisū' is a calculated scale or exponent. You cannot use it to count discrete items like people or apples.
Confusing 'shisū' with 'shihyō' in business goals. → 指標 (shihyō)
If you are setting a broad target (like 'customer happiness'), use 'shihyō.' Use 'shisū' only if you have a specific mathematical formula for it.
Saying 'shisū' when you mean 'keisū' (coefficient). → 係数 (keisū)
In math, the multiplier (e.g., 3 in 3x) is 'keisū.' The power (e.g., 2 in x²) is 'shisū.' Confusing them will lead to wrong calculations.
Pronouncing it as 'shishū'. → 指数 (shisū)
'Shishū' means embroidery. Pronouncing the second 'shi' instead of 'su' changes the meaning entirely.
Using 'shisū' for a raw measurement like height. → 数値 (sūchi) or 身長 (shinchō)
Raw physical measurements are 'sūchi' (numerical values). 'Shisū' is reserved for calculated ratios like BMI.

Tips

Suffix Power

Remember that 'shisū' often acts as a suffix. If you want to talk about a specific scale, try putting the topic before 'shisū.' This works for 'happiness,' 'unhappiness,' 'productivity,' and more.

Exponent vs Base

In math, the base is 'tei' (底) and the exponent is 'shisū' (指数). Keeping these two separate will help you explain mathematical concepts clearly in Japanese.

Watch the Weather

Weather reports are the best place to hear 'shisū' used naturally. Look for the 'Sentaku' (laundry) or 'UV' icons on screen and listen for how the announcer describes the numbers.

Kanji Logic

The kanji '指' (point) is also in 'yubi' (finger). Think of the index as a 'finger' pointing to a specific value on a ruler. This visual will help you remember the meaning.

Particle Choice

When an index moves on its own (like the stock market), use 'ga' (指数が上がる). When you or a company changes it, use 'o' (指数を改定する). This distinction is vital for B2 learners.

Precision

Use 'shisū' when you have a specific number in mind. If you are just talking about a general feeling or trend without data, use 'keikō' (tendency) or 'yōsu' (state) instead.

Long Vowel

Do not rush the 'sū.' It needs to be a full two beats (su-u). If you say 'shisu,' it sounds like a different word or simply incorrect. Practice saying 'shi-su-u' slowly.

Professional Reports

In business writing, 'shisū' is often paired with 'sanshutsu' (calculation). Instead of saying 'shisū o keisan suru,' use 'shisū o sanshutsu suru' for a more professional tone.

Comparison

Indices are useless without comparison. Always pair 'shisū' with words like 'hikaku' (comparison), 'zen-nen-hi' (compared to last year), or 'kijun' (standard).

Standardization

Japan loves standardized indices. From 'Deviation Values' (hensachi) in schools to 'Price Indices' in markets, understanding 'shisū' is a gateway to understanding Japanese social structure.

Memorize It

Mnemonic

Think of a 'pointing' (指) 'number' (数). It points to how high the stock market or the temperature is.

Visual Association

Imagine a giant finger pointing at a number on a graph. That finger is the 'shi' (指) and the number is the 'sū' (数).

Word Web

Statistics Nikkei Exponents UV Index Math Economics Growth Comparison

Challenge

Try to find three different 'shisū' in a Japanese weather app or news site today. Write them down and explain what they measure.

Word Origin

Composed of two Kanji: '指' (shi) meaning 'to point' or 'to indicate' and '数' (sū) meaning 'number' or 'count.'

Original meaning: A number that points to or indicates a specific state or magnitude.

Sino-Japanese (Kango).

Cultural Context

No specific sensitivities; it is a neutral technical term.

In English, 'Index' is used similarly, but 'Exponent' is a completely different word. Japanese uses 'shisū' for both, which can be confusing for English speakers.

Nikkei 225 (Nikkei Heikin Kabuka Shisū) TOPIX (Tōshō Kabuka Shisū) BMI (体格指数)

Practice in Real Life

Real-World Contexts

Finance/Stocks

株価指数 (Stock index)
指数の寄与度 (Index contribution)
指数先物 (Index futures)
指数連動型 (Index-linked)

Weather Forecast

不快指数 (Discomfort index)
紫外線指数 (UV index)
洗濯指数 (Laundry index)
熱中症指数 (Heatstroke index)

Mathematics

指数法則 (Laws of exponents)
指数方程式 (Exponential equation)
底と指数 (Base and exponent)
指数関数 (Exponential function)

Health/Science

体格指数 (BMI)
知能指数 (IQ)
生存指数 (Survival index)
汚染指数 (Pollution index)

Economics

消費者物価指数 (CPI)
企業物価指数 (PPI)
実質賃金指数 (Real wage index)
景気動向指数 (Business index)

Conversation Starters

"最近の物価指数についてどう思いますか？ (What do you think about the recent price indices?)"

"日本の不快指数は、夏の間本当に高いですね。 (The discomfort index in Japan is really high during the summer, isn't it?)"

"投資をする時、どの指数を一番参考にしますか？ (When you invest, which index do you refer to the most?)"

"数学の授業で指数の計算は得意でしたか？ (Were you good at exponent calculations in math class?)"

"今日の紫外線指数は高いので、日焼け止めが必要ですよ。 (The UV index is high today, so you need sunscreen.)"

Journal Prompts

今日の自分の『幸福指数』を1から100で表すといくらですか？その理由も書いてください。 (If you represented your 'Happiness Index' today from 1 to 100, what would it be? Write the reason too.)

最近、指数関数的に成長したと感じる自分のスキルは何ですか？ (What skill of yours do you feel has grown exponentially recently?)

物価指数が上がることによる、あなたの生活への影響を述べてください。 (Describe the impact on your life of the rising price index.)

あなたが新しい『指数』を作るとしたら、何を測る指数にしますか？ (If you were to create a new 'index,' what would it measure?)

ニュースで見た気になる経済指数について、自分の意見を書いてください。 (Write your opinion about an economic index you saw in the news that caught your attention.)

Frequently Asked Questions

10 questions

No, it is equally common in mathematics to mean 'exponent' or 'power.' It is also used in meteorology for various weather scales like the UV index. The meaning depends entirely on the context of the conversation.

You use the counter 'jō' (乗). For example, '2 to the power of 3' is '2の3乗' (ni no san-jō). The number 3 itself is called the 'shisū.' This is a standard way to express mathematical powers.

Generally, no, unless you are discussing specific lifestyle indices like the laundry index (sentaku shisū) or discomfort index (fukai shisū). In those cases, it's very natural. Otherwise, it sounds quite formal or technical.

Think of 'shisū' (index) as a specific math formula (like 100 + X%). Think of 'shihyō' (indicator) as a broader goal or sign. A stock index is a 'shisū,' but high unemployment is an 'indicator' of a bad economy.

Setting the base year to 100 makes it easy to see percentage changes at a glance. If the current index is 105, you know immediately that there has been a 5% increase. This is a standard practice in Japanese statistics.

No, for a count of people, use 'ninzū' (人数) or 'kazu' (数). 'Shisū' is only for calculated scales or mathematical powers. Saying 'people shisū' would be incorrect and confusing.

It means 'to index' or 'to convert into an index.' It's the process of taking different types of data and calculating a single comparable numerical scale from them. It's common in data analysis.

Yes, it is the standard term for IQ in Japanese. However, in casual talk, people often just say 'IQ' (pronounced as letters). 'Chinō shisū' is used in more formal or psychological contexts.

It's a formula involving temperature and humidity. In Japan, a 'fukai shisū' over 80 is considered very uncomfortable, and you will often hear this number on summer weather reports.

It means 'exponential function.' In popular culture, it is used to describe anything that grows extremely fast, much like the phrase 'growing exponentially' in English. It's a very common high-level metaphor.