seikai-vs-machigai

How do you say “correct” and “wrong” in Japanese? 正解 (seikai) and 間違い (machigai) are words you will hear constantly — in classrooms, quiz shows, tests, and everyday conversation. But they work differently grammatically, and there are a few related words that English speakers often confuse with them. This guide covers everything you need.

Yuka

Quick question, Rei — when should I use seikai versus machigai?

Rei

Ah, a classic mix-up! They’re related but definitely not interchangeable. I’ll explain with examples and it’ll make perfect sense.

At a Glance

Key insight: 正解 (seikai) is primarily a noun meaning “the correct answer.” 間違い (machigai) is also a noun, derived from the verb 間違う (machigau = to be mistaken). Both can be used predicatively with だ/です.

What Does 正解 (Seikai) Mean?

正解 (せいかい) means the correct answer or simply correct / right. It is most commonly used as a noun but also appears in set expressions that function like adjectives or predicates.

Kanji breakdown: 正 (sei) = “correct / straight” + 解 (kai) = “answer / solve.” Together: “the correct solution.”

Example 1

三つ、正解だね。
Mittsu, seikai da ne.
You’ve gotten three right.

Example 2

全部正解に聞こえます。
Zenbu seikai ni kikoemasu.
Everything sounds correct to me.

Example 3

どれが正解か分かりません。
Dore ga seikai ka wakarimasen.
I’m not sure which one is right.

Example 4

全問正解の人？
Zenmon seikai no hito?
Who got all the answers correct?

What Does 間違い (Machigai) Mean?

間違い (まちがい) means a mistake, an error, or a wrong answer. It comes from the verb 間違う (machigau), meaning “to be mistaken / to make an error.” The noun form 間違い is used to refer to a specific mistake or incorrect answer.

Kanji breakdown: 間 (ma) = “space / between” + 違い (chigai) = “difference / being wrong.” Together: “being off / being in error.”

Example 1

三つ、間違いだね。
Mittsu, machigai da ne.
You’ve gotten three wrong.

Example 2

全部間違いに聞こえます。
Zenbu machigai ni kikoemasu.
Everything sounds incorrect to me.

Example 3

間違いに気づかなかった。
Machigai ni kizukanakatta.
I didn’t notice the mistake.

Example 4

間違いなくあの人だよ。
Machigai naku ano hito da yo.
That’s definitely that person — no mistake about it.

Seikai vs. Machigai: Side-by-Side Comparison

Related Words: The Full “Correct / Wrong” Family

Japanese has several words related to correctness and error. Here is how they differ:

Verb nuance note:

道を間違った。(Michi wo machigatta.) = I took the wrong road. (The road itself was wrong)
道を間違えた。(Michi wo machigaeta.) = I made a mistake with the road. (I, the subject, made the error)

Both are natural in everyday speech, but 間違える emphasizes the speaker’s own action/error.

Decision Flowchart: Seikai or Machigai?

Are you describing whether something is right or wrong?
                  |
                  Yes
                  |
Is it the RIGHT answer / correct solution?
       |                    |
      Yes                   No
       |                    |
   正解 (seikai)        Is it a MISTAKE or incorrect answer?
   = correct                |                  |
                           Yes                 No → Use 正しい/間違っている for general truths
                            |
                       間違い (machigai)
                       = mistake / wrong

Important distinction for English speakers: 正解 is specifically about answering a question correctly (like on a test or in a quiz). For general “correctness” of facts or behavior, Japanese speakers often use 正しい (tadashii) instead:

Your answer on the quiz → 正解 / 間違い
A general fact being true/false → 正しい (correct) / 間違っている (wrong)

Quick Quiz: Fill in the Blank

Choose 正解 (seikai) or 間違い (machigai) — or their related forms — for each sentence. Answers below.

Q1. ３問中２問＿＿でした。
I got 2 out of 3 _____.

Q2. この書類に＿＿があります。確認してください。
There is a _____ in this document. Please check it.

Q3. ＿＿なく、彼女が犯人です。
_____ a doubt, she is the culprit.

Q4. 全問＿＿！すごいね！
Perfect score — all _____! Amazing!

Q5. 電話番号を＿＿えてしまいました。
I _____ the phone number.

Answers:

A1. 正解 — Got 2 answers correct on a quiz → ３問中２問正解でした。

A2. 間違い — An error in a document → この書類に間違いがあります。

A3. 間違い — 間違いなく is a set phrase meaning “without a doubt” → 間違いなく、彼女が犯人です。

A4. 正解 — 全問正解 = perfect score (all answers correct) → 全問正解！

A5. 間違え (間違えた) — The transitive verb 間違える (to make a mistake doing something) → 電話番号を間違えてしまいました。

Summary

正解 and 間違い are opposites, but each comes with its own grammar family. The key is to remember that 正解 focuses on the correct answer, while 間違い and its verb forms focus on the act or state of being wrong.

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