答える vs 返事
JLPT N5 vocabulary · what is the difference?
答える is a verb and 返事 is a noun, so they do not fit the same slot: you say 質問に答える but 返事をする. In meaning, 答える is giving the content of an answer — the information asked for — while 返事 is the act of responding at all, such as replying to an email or calling back when your name is read out.
When to use each
答える
こたえる
Use 答える when you supply the content of an answer. What is answered takes に: 質問に答える, 先生に答える. Never 質問を答える.
この質問に日本語で答えてください。
このしつもんににほんごでこたえてください。
Please answer this question in Japanese.
だれも答えられませんでした。
だれもこたえられませんでした。
Nobody could answer.
返事
へんじ
Use 返事 as a noun for a response coming back: 返事をする, 返事が来る, 返事を待つ. 返事する without を is also normal in speech. It covers letters, messages and answering when you are addressed.
まだ返事をもらっていません。
まだへんじをもらっていません。
I still have not had a reply.
呼んだらすぐに返事をしてね。
よんだらすぐにへんじをしてね。
Answer right away when I call you, okay?
Sentences where only one works
先生の質問に答えました。
せんせいのしつもんにこたえました。
I answered the teacher's question.
You produced the information asked for, so 答える. 返事をしました would only say you responded, not that you knew the answer.
メールの返事がまだ来ません。
メールのへんじがまだきません。
The reply to my email has not come yet.
A reply is a thing that arrives, so a noun is needed here; 答える cannot occupy this slot.
名前を呼ばれたら返事をしてください。
なまえをよばれたらへんじをしてください。
Please answer when your name is called.
Saying "here" is responding, not answering a question, so 返事. 答えてください would imply a question had been asked.
その質問には答えたくありません。
そのしつもんにはこたえたくありません。
I do not want to answer that question.
答える conjugates freely as a verb; 返事 needs する before it can do the same work.
Common mistakes
質問を答えます。
質問に答えます。
答える marks what is answered with に, not を. This is the most common error with this verb.
メールに答えます。
メールに返事をします。／メールに返信します。
答える supplies the content of an answer; replying to a message is 返事 or, in business writing, 返信.
先生に返事をしました。
先生の質問に答えました。
If the point is that you gave an answer in class, 答える is correct. 先生に返事をする suggests you merely acknowledged being spoken to.
Frequently asked questions
Can I say 返事する without を?
Yes. 返事する is normal in conversation; 返事をする is slightly more careful and is what you would write.
What is the noun form of 答える?
答え (こたえ) — the answer itself, as in 答えが分かりません. That is the content; 返事 is the act of responding.
Is 返信 different from 返事?
返信 is specifically a written reply to a message or letter and is the usual word in business email. 返事 is broader and more everyday.