Translation guide
The English word "probability" can refer to the mathematical concept, the likelihood of an event, or an informal sense of something being likely. In Japanese, different words and expressions are used depending on the context and level of formality.
Expressing the precise, numerical chance of an event occurring, often in academic, scientific, or technical contexts.
The standard term for mathematical probability. Used in statistics, science, and everyday talk about chances.
降水確率は80%です。
The probability of rain is 80%.
この事象が起こる確率を計算してください。
Please calculate the probability of this event occurring.
A formal, academic term for probability, often used in philosophy, law, or statistics. Less common in everyday speech.
この理論の蓋然性は高い。
The probability of this theory is high.
Talking about how likely something is to happen in daily life, without precise numbers.
The most common word for 'possibility' or 'likelihood'. It can be used in both formal and casual contexts.
成功する可能性は低い。
The probability of success is low.
彼が来る可能性はある？
Is there any probability that he will come?
Often used for prospects or expectations, implying a reasonable chance based on some evidence.
A formal expression meaning 'there is a strong probability that...'. Used in news or official statements.
景気が後退する公算が大きい。
There is a high probability that the economy will decline.
Conveying that something is probable without using a noun.
The most common way to say 'probably'. Often used with ～だろう or ～と思う.
たぶん明日は雨だろう。
Probably it will rain tomorrow.
A more formal version of 'probably', often used in writing or speeches.
Literally 'the probability is high that...'. Used in both casual and formal contexts.
彼が遅刻する確率が高い。
The probability that he will be late is high.
Emphasizing that something is almost certain.
An idiomatic phrase meaning 'in all probability' or 'nine times out of ten'.
十中八九、彼は合格するだろう。
In all probability, he will pass the exam.
Literally 'almost certainly without mistake'. Very common in speech.
まず間違いなく彼は来るよ。
In all probability, he will come.
確率 (kakuritsu) is used for numerical, calculable probability, while 可能性 (kanousei) is broader and refers to possibility or likelihood in general. Use 確率 when you can assign a number or percentage; use 可能性 for more qualitative chances.
蓋然性 (gaizensei) is very formal and technical. In most everyday situations, 確率 or 可能性 are more natural.
宝くじに当たる確率はどのくらいですか？
What is the probability of winning the lottery?
明日は雪が降る確率が高いです。
There is a high probability of snow tomorrow.
The probability of it being sunny tomorrow is slim.
おそらく彼は来ないでしょう。
Probably he will not come.