Both 内緒 (ないしょ, naisho) and 秘密 (ひみつ, himitsu) translate as “secret” in English, but they are used in different ways. Mixing them up can sound unnatural, so let’s break down when to use each one.
| 内緒 (naisho) | 秘密 (himitsu) | |
|---|---|---|
| Core meaning | Don’t tell (keeping quiet about something) | A secret / confidential information |
| Nuance | Personal, intimate — ‘keep this between us’ | A secret as a thing — information kept hidden |
| Used as | Noun / な-adjective | Noun / な-adjective |
| Register | Casual, warm | Neutral to serious |
内緒 — “Just Between Us”
内緒 carries a warm, personal feeling. It’s often used between friends or family — “let’s keep this quiet,” “don’t tell anyone,” “it’s our little secret.”
- 内緒にしてね。— Keep this a secret (between us), okay?
- これ、お母さんには内緒だよ。— This is a secret from Mom, okay?
- 内緒でプレゼントを用意した。— I prepared a present in secret.
内緒 often appears in the phrase 内緒にする (to keep secret) and 内緒で (secretly, without telling). It implies an active act of not revealing something.
秘密 — A Secret as a Thing
秘密 refers to secret information — something that is kept confidential. It is more neutral or formal, and is often used in serious or official contexts, as well as everyday speech.
- それは秘密です。— That’s a secret.
- 秘密を守る。— To keep a secret.
- 彼には秘密がある。— He has a secret.
- 国家秘密 — state secret / classified information
秘密 is also used in compounds like 秘密基地 (himitsu kichi, secret base) and 秘密兵器 (himitsu heiki, secret weapon).
Key Difference: Action vs Information
| Concept | 内緒 | 秘密 |
|---|---|---|
| ‘Keep this a secret’ (asking someone) | 内緒にしてね ✅ | Less natural here |
| ‘That’s a secret’ (information) | Both OK | 秘密です ✅ (more neutral) |
| ‘He has a secret’ | Less natural | 彼には秘密がある ✅ |
| ‘Secretly (without telling)’ | 内緒で ✅ | Less natural as adverb |
Are you asking someone to stay quiet about something?
→ 内緒にしてね (personal, warm)
Is it information being kept confidential?
→ 秘密 (neutral, can be serious)
Either works in general conversation.Natural Conversations
ねえ、聞いて！でも内緒にしてね。— Hey, listen! But keep it a secret, okay?
もちろん。何があったの？— Of course. What happened?
彼に秘密を打ち明けた。— I confided a secret to him.
大丈夫だった？ちゃんと守ってくれた？— Was it okay? Did he keep it properly?
Common Mistakes
Mistake: Using 秘密にしてね where 内緒にしてね is more natural.
✅ 内緒にしてね。 (warm, personal request between friends)
⚠️ 秘密にしてね。 (grammatically fine, but sounds slightly cold/formal between close friends)
Tip: With friends and family, 内緒 feels warmer. In business or formal contexts, 秘密 is safer.
Quick Quiz
Choose 内緒 or 秘密:
1. この話、お父さんには___にしておいて。(Keep this from Dad — personal/family context)
2. その情報は___です。(That information is confidential.)
Answers: 1. 内緒 2. 秘密
Want to improve your Japanese even faster? italki connects you with native Japanese tutors for one-on-one lessons — a great way to practice real conversations and get personalized feedback.