The core meaning
Abunai, written 危ない, is an i-adjective meaning dangerous or unsafe. It describes places, actions, objects and situations, and it conjugates normally.
It is an everyday word, used by parents, friends and passers-by rather than in official notices.
| Japanese | Romaji | Meaning |
|---|---|---|
| この道は夜、危ないです。 | Kono michi wa yoru, abunai desu. | This road is dangerous at night. |
| ナイフは危ないから気をつけて。 | Naifu wa abunai kara ki o tsukete. | Knives are dangerous, so be careful. |
| 夜の一人歩きは危ないですよ。 | Yoru no hitori-aruki wa abunai desu yo. | Walking alone at night isn't safe. |
| 危なくない場所で遊んでね。 | Abunakunai basho de asonde ne. | Play somewhere safe. |
Abunai! as a warning
On its own, abunai is the fastest warning in Japanese, the equivalent of watch out or look out. It is often followed by the specific danger or an instruction.
If you hear it, react first and ask questions later.
| Japanese | Romaji | Meaning |
|---|---|---|
| 危ない！ | Abunai! | Watch out! |
| 危ないよ！ | Abunai yo! | Careful! (to a friend or child) |
| 車、来てるよ！ | Kuruma, kiteru yo! | There's a car coming! |
| 下がってください！ | Sagatte kudasai! | Please step back! |
| 自転車、気をつけて！ | Jitensha, ki o tsukete! | Watch out for the bike! |
Abunakatta: that was close
In the past tense, abunai describes a near miss. Abunakatta is what you say after nearly tripping, nearly missing a train or nearly forgetting something important.
Abunaku with tokoro datta spells out what almost happened.
| Japanese | Romaji | Meaning |
|---|---|---|
| 危なかった！ | Abunakatta! | Phew, that was close! |
| 危なく乗り遅れるところだった。 | Abunaku noriokureru tokoro datta. | I nearly missed the train. |
| 危ないところを助けてもらいました。 | Abunai tokoro o tasukete moraimashita. | Someone helped me out of a dangerous spot. |
| ギリギリ間に合った。 | Girigiri maniatta. | I made it just in time. |
Abunai for risky and uncertain
Abunai stretches naturally from physical danger to risk and doubt. A plan can be abunai, a deadline can be abunai, and so can a company in financial trouble.
Describing a person or area as abunai suggests they are shady or best avoided.
| Japanese | Romaji | Meaning |
|---|---|---|
| その計画はちょっと危ないですね。 | Sono keikaku wa chotto abunai desu ne. | That plan seems a bit risky. |
| 締め切り、ちょっと危ないかも。 | Shimekiri, chotto abunai kamo. | We might not make the deadline. |
| 今の成績だと、合格は危ないです。 | Ima no seiseki da to, gōkaku wa abunai desu. | With current grades, passing is in doubt. |
| 危ない話には乗らないほうがいいよ。 | Abunai hanashi ni wa noranai hō ga ii yo. | Better not to get involved in shady deals. |
Keeping other people safe
Abunai is also the word you reach for when you are the one giving the warning: to a child near a road, a friend on an icy step, or a guest in an unfamiliar building. Pairing it with kara or node turns the warning into a reason, which sounds calmer and more helpful than a single shout.
Staff at stations, events and construction sites use polite versions of the same pattern, so recognising them also helps you follow instructions in a crowd.
| Japanese | Romaji | Meaning |
|---|---|---|
| 危ないから、ここで待っててね。 | Abunai kara, koko de mattete ne. | It's not safe, so wait here, okay? |
| 危ないので、手すりにつかまってください。 | Abunai node, tesuri ni tsukamatte kudasai. | Please hold the handrail, for your safety. |
| 道が凍っているので、気をつけてください。 | Michi ga kōtte iru node, ki o tsukete kudasai. | The road is icy, so please be careful. |
| 危ないので、お下がりください。 | Abunai node, o-sagari kudasai. | For your safety, please step back. |
| お子様の手を離さないでください。 | O-kosama no te o hanasanaide kudasai. | Please keep hold of your child's hand. |
Kara sounds natural with friends and family, and node sounds more polite. Both explain why, and a reason makes people far more likely to follow a warning than an order does.
Safety signs and announcements
Official notices rarely use abunai. They prefer the formal kiken, or short compounds that name the specific hazard. Recognising a handful covers most of what you will see.
| Japanese | Romaji | Meaning |
|---|---|---|
| 危険 | kiken | Danger |
| 立入禁止 | tachiiri kinshi | No entry |
| 足元注意 | ashimoto chūi | Watch your step |
| 頭上注意 | zujō chūi | Mind your head |
| 駆け込み乗車は危険ですのでおやめください。 | Kakekomi jōsha wa kiken desu node o-yame kudasai. | Rushing onto the train is dangerous, so please don't. |
| 黄色い線の内側までお下がりください。 | Kiiroi sen no uchigawa made o-sagari kudasai. | Please stand behind the yellow line. |
Abunai, kiken and yabai
These three overlap, but they belong to different registers and have drifted apart in meaning.
| Japanese | Romaji | Meaning |
|---|---|---|
| ここは危ないです。 | Koko wa abunai desu. | It's dangerous here. |
| 危険物 | kikenbutsu | Hazardous materials |
| やばい、遅刻する！ | Yabai, chikoku suru! | Oh no, I'm going to be late! |
| Word type | Register | Typical use |
|---|---|---|
| The everyday word for dangerous | Neutral spoken | Warnings, risky situations, close calls |
| The formal word for danger | Written and official | Signs, announcements, reports |
| The slang word that once meant dangerous | Casual, young | Any strong reaction, good or bad |