dangerous

dangerous — adjective

1. Someone or something that is dangerous can easily hurt you. The word describes p

1.adjectiveA2
Definition

Someone or something that is dangerous can easily hurt you. The word describes people, animals, objects, places, or actions that are not safe because they threaten your body or your life.

Example

Walid was warned not to swim in the river because the current was dangerous.

The old staircase was so dangerous that the landlord finally agreed to fix it.

so + adjective + that clause for result

Common collocations
  • dangerous animal
  • dangerous road
  • dangerous situation
  • dangerous driving
  • dangerous weapon
  • dangerously close
Synonyms
  • hazardous

    more formal; often describes materials, conditions, or work environments rather than people or animals

  • unsafe

    focuses on lack of safety or protection; common for buildings, products, or roads

  • risky

    implies a choice with uncertain outcome; usually less severe than 'dangerous'

  • perilous

    formal or literary; suggests a very high level of danger

Antonyms
  • safe

    the most common opposite; free from danger or risk

  • harmless

    unable to cause harm; often used for animals or substances

Grammar Patterns

be + dangerous

dangerous + noun

it is dangerous + to-infinitive

so + dangerous + that clause

Usage Note

Frequently describes people, animals, objects, places or activities that pose a direct physical threat. The most common patterns are 'be + dangerous' (The dog is dangerous) and 'dangerous + noun' (a dangerous road).

Common Mistakes

The chemicals are danger to humans.
The chemicals are dangerous to humans.
'danger' is a noun; 'dangerous' is the adjective form.
I am dangerous to walk alone at night.
It is dangerous to walk alone at night.
Use the 'it is dangerous + to-infinitive' pattern, not a personal subject.

2. Used when a situation, decision, or idea is likely to lead to trouble, loss, or

2.adjectiveB1
Definition

Used when a situation, decision, or idea is likely to lead to trouble, loss, or other negative outcomes, even though no one is at risk of physical injury or death.

Example

Eleni knew that spreading rumours about her colleague was a dangerous game to play.

collocation: a dangerous game

It can be dangerous for a company to ignore customer complaints for too long.

it + be + dangerous + for + noun + to-infinitive

Common collocations
  • dangerous game
  • dangerous precedent
  • dangerous move
  • dangerous strategy
  • dangerous territory
  • dangerous ground
Synonyms
  • risky

    common alternative; focuses on uncertainty of outcome rather than severity of harm

  • problematic

    less severe; suggests difficulties rather than real danger

  • dicey

    informal; describes a situation that may go wrong

Antonyms
  • safe

    the general opposite; not likely to cause problems

  • sound

    describes a sensible decision or plan that will not cause trouble

Grammar Patterns

be + dangerous

dangerous + abstract noun

it is dangerous + for + noun + to-infinitive

dangerous + to + noun phrase

Usage Note

Often used with abstract nouns such as 'game', 'move', 'step', 'policy', or 'precedent' to describe choices or situations that create the risk of a bad outcome. Unlike sense 1, the risk here is to reputation, money, relationships, or stability — not to physical safety.

Common Mistakes

The stock market is a dangerous place.' (when referring to financial risk, this could be confused with physical danger)
Investing in the stock market without research is a dangerous strategy.
Specify the abstract risk to avoid confusion with physical danger.
Idioms

a dangerous game

idiom

A situation where someone takes risks, often to get an advantage.

Maya knew she was playing a dangerous game with her boss.

Is Brian playing a dangerous game by investing all his savings?

dangerous ground

idiom

A topic or situation that could make someone angry or cause problems.

Diego realized he was on dangerous ground when he mentioned politics.

Sara avoided dangerous ground by not asking about her friend's divorce.

Word family

Synonym discussion

Sense: adjective/1

The core meaning these four words share is 'not safe,' but they differ in register and scope. 'Dangerous' is the broadest and most neutral word — it fits any context from a child's playground to a war zone. 'Hazardous' is more formal and technical; it often describes materials, conditions, or work environments (hazardous waste, hazardous driving conditions). 'Unsafe' focuses on inadequate protection rather than inherent threat — a building can be unsafe because its fire exits are blocked, even though the building itself is not dangerous. 'Risky' implies voluntary choice with uncertain outcome and is usually less severe ('a risky investment' might lose money but won't injure you). 'Perilous' is the strongest and most literary word; it suggests that death or serious harm is likely. For everyday safety warnings, 'dangerous' or 'unsafe' are the best choices; for formal documents, 'hazardous' is more appropriate.

hazardous ↗risky ↗unsafe ↗perilous

Common collocations

Nouns

  • dangerous situation
  • dangerous condition
  • dangerous driving
  • dangerous animal
  • dangerous weapon
  • dangerous game
  • dangerous precedent

Adverbs

  • extremely dangerous
  • potentially dangerous
  • highly dangerous
  • politically dangerous
  • socially dangerous
  • inherently dangerous

Phrases

Prepositions

  • dangerous to
  • dangerous for

Etymology

LatinVulgar LatinOld FrenchAnglo-NormanEnglish

The word 'dangerous' entered English in the 13th century from Old French 'dangerous' (also 'dangereus'), which had the meaning 'difficult to deal with, arrogant, or lordly.' The root is Old French 'dangier' meaning 'power, dominion, or authority,' which came from Vulgar Latin '*dominiarium' ('power of a lord'), based on Latin 'dominus' ('lord, master'). The shift in meaning from 'exercising lordly power' to 'posing a risk or threat' reflects the idea that being under someone's absolute control left you vulnerable to harm. By the late 14th century, the modern sense of 'causing or involving risk' was firmly established in English.