Translation guide
In Japanese, expressing tautology (saying the same thing twice in different words) is often avoided in formal writing but can be used for emphasis, clarification, or stylistic effect in casual speech. This guide covers common patterns for redundant expressions, logical tautologies, and rhetorical repetition.
The speaker uses two words or phrases that mean essentially the same thing, often for emphasis or out of habit.
Used to say 'A is also A', often implying that something is typical or expected, sometimes with a nuance of criticism or resignation.
あの人はあの人だ。
He's just being himself. (That's just how he is.)
Literally 'to repeat the same thing', used to point out tautology in speech or writing.
彼の説明は同じことを繰り返しているだけだ。
His explanation is just repeating the same thing.
A technical term for 'double expression' or 'redundant phrase', often discussed in writing guides.
「頭痛が痛い」は二重表現の例だ。
'My headache hurts' is an example of a redundant expression.
A statement that is true by necessity or by its logical form, often used in philosophy or mathematics.
The standard term for a logical tautology in philosophy and mathematics.
「PまたはPでない」は恒真式である。
'P or not P' is a tautology.
Repeating the same idea in different words to reinforce a point, common in speeches or persuasive writing.
Means 'in other words', often used to restate something for clarity, which can create a tautology if the restatement adds no new information.
彼は正直者だ。言い換えれば、嘘をつかない人だ。
He is an honest person. In other words, he doesn't lie.
Means 'that is to say' or 'in short', used to summarize or rephrase, sometimes resulting in tautology.
彼は無職だ。つまり、仕事がない。
He is unemployed. That is, he has no job.
In Japanese, certain combinations like 「馬から落馬する」(fall off a horse from a horse) or 「後で後悔する」(regret later afterwards) are considered awkward tautologies. Be mindful of compound words that already contain the meaning you're adding.
Patterns like 「AはAだ」 are not considered poor style in casual Japanese; they are a natural way to express inevitability or acceptance. Use them freely in conversation.
The loanword from English, used in academic contexts.
この命題はトートロジーだ。
This proposition is a tautology.
Literally 'same word repetition', sometimes used for logical tautology but more often for rhetorical repetition.
その議論は同語反復に過ぎない。
That argument is nothing but a tautology.