What does 'red flag' mean?

What it means: A warning sign or signal that something is wrong, risky, or potentially problematic. A red flag indicates you should pay attention and investigate further.

"That contract clause is a major red flag."
"Her evasive answers during the interview were red flags."
"I ignored all the red flags early on."

Where it comes from: Red flags are literally warning signals — used at beaches, motor races, and military contexts to signal danger. The metaphor transferred to any situation where a warning sign appears.

Degrees of severity: A "red flag" can be anything from a minor concern to a serious warning. Context tells you how urgent it is. "A bit of a red flag" = a concern. "A massive red flag" = a serious warning.

Recently: The term has expanded significantly in relationship and dating contexts — people discuss "red flags" in potential partners constantly. "Green flags" (positive signs) emerged as the opposite.

Register: Casual to professional. Now ubiquitous in all contexts.

Tags: business English, warning signs, relationships, everyday English