hazardous

hazardous — adjective

1. describing a substance, activity, or situation that could harm people's health,

1.adjectiveB2
Definition

describing a substance, activity, or situation that could harm people's health, damage property, or cause serious injury.

Example

The abandoned factory was classified as hazardous after the inspection team arrived.

passive: was classified as hazardous

Sade wore protective gear while handling hazardous waste at the chemical plant.

collocation: hazardous waste

Common collocations
  • hazardous waste
  • hazardous materials
  • hazardous conditions
  • hazardous to health
  • hazardous to the environment
  • hazardous substance
  • hazardous chemicals
  • hazardous area
Synonyms
  • dangerous

    broader and more common in everyday speech; 'dangerous' can apply to anything that might cause harm, while 'hazardous' often implies a specific, recognized risk

  • risky

    focuses on the chance of failure or loss rather than physical danger; a risky investment may not be hazardous to your health

  • unsafe

    stresses lack of security or protection; a building can be unsafe because of poor construction without necessarily involving hazardous materials

Antonyms
  • safe

    free from danger or risk; the opposite of hazardous in nearly all contexts

  • harmless

    unable to cause injury or damage; a harmless substance is one that poses no health risk

Grammar Patterns

hazardous + noun (hazardous waste / hazardous materials / hazardous conditions)

be + hazardous

hazardous to + noun phrase

Usage Note

Common in safety regulations, environmental protection, and industrial contexts rather than everyday casual speech. Often appears in compound nouns such as hazardous waste, hazardous materials (abbreviated hazmat), and hazardous conditions.

Common Mistakes

The dog is hazardous.
The dog is dangerous.
'hazardous' is used for substances, conditions, or activities, not for animals or people.
This knife is hazardous to cut vegetables.
This knife is dangerous for cutting vegetables.
'hazardous' typically describes materials or conditions, not tools used for their normal purpose.

Word family

  • hazard
    nounB1
  • hazard
    verbC1
  • hazardously
    adverbC1
  • hazardousness
    nounC2

Synonym discussion

Sense: adjective/1

Hazardous, dangerous, risky, unsafe, and perilous all describe potential harm, but they differ in scope and register. Dangerous is the broadest word, covering anything that might cause injury, loss, or damage (a dangerous road, a dangerous idea). Hazardous is more specific to materials, conditions, or activities that pose a recognized health or safety risk, often in official or technical contexts (hazardous waste, hazardous working conditions). Risky focuses on the probability of failure or negative outcome rather than physical danger (a risky business venture). Unsafe stresses lack of protection or security and is common for buildings, products, or practices that fail to meet safety standards. Perilous is the most literary and dramatic, suggesting an immediate, life-threatening situation (a perilous journey across the frozen lake). In everyday speech, dangerous is usually the best choice; in formal or regulatory writing, hazardous is more precise.

dangerous ↗risky ↗unsafe ↗perilous

Common collocations

Nouns

Adverbs

  • highly hazardous
  • potentially hazardous
  • extremely hazardous
  • inherently hazardous

Phrases

  • pose a hazardous risk
  • classified as hazardous
  • deem something hazardous

Prepositions

  • hazardous to

Etymology

Old FrenchMiddle EnglishEnglish

Comes from the noun 'hazard' (a game of chance played with dice, from Old French 'hasard'), combined with the suffix '-ous' meaning 'full of'. The original gambling sense shifted in Middle English to mean 'risk' or 'danger', giving us the modern meaning of something that carries potential harm.