Translation guide
A warning sign or indicator of a problem, danger, or undesirable trait, often used in relationships, business, or safety contexts.
To describe a behavior or trait that signals potential problems in a person or relationship.
Literally 'danger signal', this is the most direct and common translation for 'red flag' in the sense of a warning sign in relationships or situations.
彼の態度は危険信号だ。
His attitude is a red flag.
Loanword from English, commonly used in casual conversation, especially among younger people or in online contexts.
それってレッドフラッグじゃない？
Isn't that a red flag?
Means 'a sign to be wary of', slightly more formal and explanatory.
その行動は警戒すべきサインです。
That behavior is a red flag.
To refer to any sign that something is wrong or risky, such as in business, health, or safety.
General term for 'warning sign', applicable in many contexts.
この症状は警告サインかもしれません。
This symptom might be a red flag.
Means 'dangerous sign' or 'ominous indication', slightly more serious tone.
経済の危険な兆候が現れている。
Red flags are appearing in the economy.
To refer to a physical red-colored flag, such as in sports or signaling.
Standard term for a red flag as an object.
審判が赤旗を上げた。
The referee raised a red flag.
危険信号 is the standard Japanese term and is understood by all ages. レッドフラッグ is a loanword popular among younger generations and in online communities, but may sound casual or trendy.
あの人の嘘は危険信号だ。
That person's lies are a red flag.
それ、レッドフラッグだよ。
That's a red flag.