dangerous
- 1Involving risk or likely to cause harm, injury, or damage.
Drunk drivers are dangerous to everyone else on the road.
She warned the tenants that the frayed wiring was dangerous.
UsageDangerous to or for the people at risk; it's dangerous to + verb: it's dangerous to swim here.
Note
Here the danger comes from someone or something with the power to hurt, which fits the word's early history. Middle English dangerous could mean domineering or arrogant, and Old French dangereus meant threatening. Thomas Southerne's Oroonoko (1696) applies it to a man his enemies have decided is a threat. Frank Herbert's Dune (1965) stretches it to knowledge itself: dangerous facts.
Checked 5 Nov 2026 · 6 facts
- Middle English dangerous could mean domineering or arrogant. en.wiktionary.org
- Old French dangereus meant threatening. en.wiktionary.org
- Thomas Southerne wrote Oroonoko, published in 1696. en.wikipedia.org
- Oroonoko uses dangerous of a man regarded as a threat by his enemies; Aboan addresses Oroonoko. scalar.usc.edu
- Frank Herbert wrote Dune, first published as a book in 1965. en.wikipedia.org
- Dune contains the phrase dangerous facts, in the Duke's thoughts. en.wiktionary.org
- 2In serious danger of dying, especially from illness; in a critical condition.
Similarcritical
Note
A sickroom word, said of the patient rather than of any hazard: a doctor who called someone dangerous meant they might not live. It is dated and colloquial, and it stands after the verb (the patient was dangerous) rather than before a noun. A listener today would hear the "ready to do harm" meaning, so present-day speakers say dangerously ill or in critical condition instead.
Checked 5 Nov 2026 · 1 fact
- Dangerous formerly described someone in danger of death from illness. en.wiktionary.org
Use it in a sentence
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Origin
From Middle English dangerous (meaning difficult, severe, or full of danger), borrowed through Anglo-Norman from Old French dangereus ("threatening, difficult"), from dangier. It is equivalent to danger plus the suffix -ous, and it replaced the native Old English word frēcne.
Checked 5 Nov 2026 · 5 facts
- Dangerous descends from Middle English dangerous, which had the meanings difficult, severe, and full of danger. en.wiktionary.org
- The Middle English word was borrowed through Anglo-Norman from Old French. en.wiktionary.org
- Old French dangereus meant threatening or difficult and derived from dangier. en.wiktionary.org
- Dangerous is equivalent to danger plus the suffix -ous. en.wiktionary.org
- Dangerous displaced the native Old English word frēcne. en.wiktionary.org