確率

• 読み: かくりつ
• ローマ字: kakuritsu
• 漢字の分解: 確 (kaku) — certain, definite; 率 (ritsu) — rate, ratio
• 発音: /ka.kɯ.ɾi.tsɯ/

意味

Probability; likelihood. A numerical measure of the likelihood that a given event will occur, expressed as a value between 0 and 1.

One of the most fundamental concepts in mathematics and statistics. 確率論 (probability theory) underpins statistics, quantum mechanics, information theory, and finance. In everyday Japanese, 確率 is commonly used to express odds or chances (e.g., 雨が降る確率は70パーセント — there is a 70% chance of rain). Related terms: 条件付き確率 (conditional probability), 確率変数 (random variable), 確率分布 (probability distribution). Distinguished from 可能性 (kanōsei — possibility), which is more informal.

例文

1. このコインを投げたとき、表が出る確率は理論上50パーセントだ。
2. 統計学における確率論は、不確実な現象を定量的に扱うための数学的基盤を提供する。
3. 機械学習モデルは各クラスに属する確率を出力し、最も高い値のラベルを予測として返す。

使い方ガイド

場面: mathematics, statistics, physics, data science, everyday language

トーン: technical to neutral

起源と歴史

Meiji-era Sino-Japanese translation: 確 (kaku) — certain, definite + 率 (ritsu) — rate, ratio. Coined to render the mathematical concept of 'probability' from Western mathematics. 率 is widely used in Japanese for ratios and rates (利率, 速率, 税率).

文化的背景

時代: Meiji-Modern

世代: All ages

社会的背景: Universal