Perigo!

You will mostly see it written in capital letters on signs. In speech, you use it to warn others. You can say it alone as an exclamation: Perigo!. Or you can describe a situation: Isso é um perigo. It works for physical threats like electricity or thin ice. It also works for metaphorical threats like a bad investment. Use a sharp, rising intonation for emergencies. Keep it calm for general warnings.

Use it when you see a high-voltage fence. Use it if a friend is driving too fast. It is perfect for hiking near a cliff edge. Use it at the beach for strong currents. In a professional setting, use it to flag a project risk. If you are texting, use it with the ⚠️ emoji. It is universal and understood by everyone instantly.

Do not use it for minor inconveniences. If you drop a spoon, it is not a perigo. If you are late for a bus, do not shout it. It is too heavy for small social awkwardness. Avoid using it sarcastically until you are very fluent. People might take you literally and panic. Save it for when real caution is required.

In Portugal and Brazil, safety signs are very standardized. Perigo is the highest level of warning. You will see it on yellow or red backgrounds. It has been the standard warning since the dawn of modern signage. It is a word that demands respect across all Lusophone cultures. There is no regional slang that replaces this in emergencies.

You might hear Cuidado! which means 'Careful!'. Cuidado is much more common for daily life. Perigo de morte means 'Danger of death'. Zona de perigo means 'Danger zone'. If someone is a 'troublemaker', they might be called um perigo. It is a versatile root word for all things risky.