Translation guide
The English word "reaction" covers a wide range of responses, from physical and chemical changes to emotional and social responses. In Japanese, different words and expressions are used depending on the context. This guide helps you choose the most natural Japanese equivalent.
Expressing how someone responds to something that happens or is said, often in a social or conversational context.
The most general and common word for "reaction." It can refer to physical, emotional, or social responses. Safe to use in most situations.
彼の冗談に誰も反応しなかった。
No one reacted to his joke.
そのニュースに対する彼女の反応は意外だった。
Her reaction to the news was surprising.
A loanword from English, often used in casual conversation or entertainment contexts. It can imply a more visible or exaggerated response, like in TV shows.
彼はいつもリアクションが大きい。
He always has big reactions.
Refers specifically to verbal responses in a conversation, often implying a back-and-forth exchange. Used for how someone replies or handles questions.
彼女の受け答えはとても丁寧だ。
Her responses are very polite.
Describing a scientific process where substances interact and change, or a physical response of the body.
Also used for chemical and physical reactions. The context makes the meaning clear.
この化学反応は熱を発生する。
This chemical reaction produces heat.
アレルギー反応が出た。
I had an allergic reaction.
Focusing on the emotional, psychological, or gut-level aspect of a reaction.
Still the most common word, but can be paired with emotional adjectives for clarity.
彼の言葉に感情的な反応をしてしまった。
I had an emotional reaction to his words.
Means "reflex," used for automatic, instinctive physical or emotional responses.
Refers to how one takes or interprets something emotionally. More about the internal processing of an event.
批判の受け止め方は人それぞれだ。
People's reactions to criticism vary.
Describing how a body or organism responds to a stimulus, drug, or treatment.
General term for medical/biological reactions.
ワクチンの副反応が心配だ。
I'm worried about vaccine reactions.
Used in medical contexts to mean "response" to treatment, e.g., "treatment response." More technical.
Expressing a negative response against change, progress, or a particular idea.
Means "opposition," "backlash," or "pushback." Used when people react negatively and resist something.
新しい規則に社員から反発があった。
There was a backlash from employees against the new rules.
Means "reaction" in the sense of a counter-movement or rebound, often political or social.
Literally "rejection reaction," used for strong negative reactions, like rejecting a foreign idea or a transplant.
反応 is the standard, all-purpose word for "reaction." リアクション is a loanword that often implies a more exaggerated or performative response, like those seen on variety shows. In formal writing or serious contexts, stick with 反応.
In English, "reaction" is often used where Japanese would use a more specific verb or phrase. For example, "What was his reaction?" might be more naturally expressed as 「彼はどう思った？」 (What did he think?) or 「彼は何て言った？」 (What did he say?) depending on context.
彼の反応が見たい。
I want to see his reaction.
彼女はその薬にアレルギー反応を起こした。
She had an allergic reaction to the medicine.
世間の反応は賛否両論だった。
The public reaction was mixed.
Specifically means "chemical reaction." Use when you need to be precise.
化学反応の速度を調べる。
Investigate the rate of the chemical reaction.
It was a reflex reaction.
治療に対する応答は良好だった。
The response to treatment was good.
改革に対する反動が起きた。
There was a reaction against the reforms.
彼の提案に拒否反応を示した。
They showed a rejection reaction to his proposal.