arsenic

American  

[ahr-suh-nik, ahrs-nik, ahr-sen-ik] / ˈɑr sə nɪk, ˈɑrs nɪk, ɑrˈsɛn ɪk /

noun

1. a grayish-white element having a metallic luster, vaporizing when heated, and forming poisonous compounds. As; 74.92; 33.

2. arsenic trioxide.

3. a mineral, the native element, occurring in white or gray masses.

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adjective

1. of or containing arsenic, especially in the pentavalent state.

arsenic British  

noun

1. a toxic metalloid element, existing in several allotropic forms, that occurs principally in realgar and orpiment and as the free element. It is used in transistors, lead-based alloys, and high-temperature brasses. Symbol: As; atomic no: 33; atomic wt: 74.92159; valency: –3, 0, +3, or +5; relative density: 5.73 (grey); melting pt: 817°C at a pressure of 3MN/m² (grey); sublimes at 613°C (grey)

2. a nontechnical name for arsenic trioxide

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adjective

1. of or containing arsenic, esp in the pentavalent state

arsenic Scientific  

/ är′sə-nĭk /

1. A metalloid element most commonly occurring as a gray crystal, but also found as a yellow crystal and in other forms. Arsenic and its compounds are highly poisonous and are used to make insecticides, weed killers, and various alloys. Atomic number 33; atomic weight 74.922; valence 3, 5. Gray arsenic melts at 817°C (at 28 atm pressure), sublimes at 613°C, and has a specific gravity of 5.73.

2. See Periodic Table

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Other Word Forms

• nonarsenic
  adjective

Etymology

Origin of arsenic

First recorded in 1350–1400; Middle English arsenicum, from Latin, from Greek arsenikón “orpiment” (a mineral), noun use of neuter of arsenikós “virile” (from ársēn “male, strong” + -ikos -ic ), probably alteration by folk etymology of a Semitic word such as Syriac zarnīkā “orpiment,” from Middle Persian (compare Persian zargūn “gold-colored”; see jargon ² ( def. ))

Explanation

Arsenic is a chemical element that's quite poisonous to humans and other animals. Arsenic was once commonly used in rat poison and insecticides. While arsenic is a naturally occurring element, it's often thought of as a poison used in mystery novels to murder people. Several kinds of agricultural bug killers once contained arsenic, but historically people have been more likely to suffer arsenic poisoning from natural leaching into water sources, like wells, or as a side effect of mining. Arsenic has a Greek root, arsenikon, from the Middle Persian zarnik, "gold colored."

Example Sentences

The second-guessing could extend even to long-settled standards, environmental scientists said, such as how much arsenic is allowed in drinking water and how much lead is acceptable in paint and soil.

From Salon • May 5, 2026

Producing rare earths requires heavy chemicals and can produce toxic waste, with cases including illegal operations polluting Mekong tributaries in Myanmar, Laos and Cambodia with arsenic and cadmium.

From Barron's • Apr. 22, 2026

A Consumer Reports review of 41 types of powdered infant formula last year found that about half contained detectable levels of contaminants such as arsenic, lead and “forever chemicals” known as PFAS.

From The Wall Street Journal • Feb. 17, 2026

Lead is the heaviest of the heavy metals and, like mercury and arsenic, it accumulates in living tissue and is harmful even at low concentrations.

From Science Daily • Feb. 7, 2026

However, one detail perturbed him: suppose autopsies revealed the presence of arsenic?

From "In Cold Blood" by Truman Capote