arsenic

noun

ar·​se·​nic

ˈärs-nik, 

ˈär-sə- 

1

: a solid chemical element that is used especially in wood preservatives, alloys, and semiconductors and is extremely toxic in both pure and combined forms see Chemical Elements Table

2

: a poisonous trioxide As₂O₃ or As₄O₆ of arsenic used especially as an insecticide or weed killer

called also arsenic trioxide

Examples of arsenic in a Sentence

Recent Examples on the Web

Researchers detected 16 airborne metals including lead, zinc, nickel and arsenic, Jerrett said. —Tony Briscoe, Los Angeles Times, 4 June 2026

Electronic waste may expose humans and the environment to lead, mercury, arsenic, flame-retardant chemicals and other contaminants, according to the Geneva Environment Network. —Greta Cross, USA Today, 2 June 2026

The Eaton Fire destroyed 9,400 homes and structures in the Altadena area in January 2025 and sent smoke containing lead, arsenic and asbestos into the air and to settle nearby. —Evan Bush, NBC news, 20 May 2026

Charles Darwin used spirits of wine, sometimes strengthened with alum, arsenic, or mercuric chloride, during his voyage on the HMS Beagle (1831–1836). —Matthew Wills, JSTOR Daily, 18 May 2026

Word History

Etymology

Middle English arsenek, arsenic "any of various compounds of arsenic, as yellow orpiment (arsenic trisulfide)," borrowed from Anglo-French & Latin; Anglo-French arsenik, arsneke, borrowed from Latin arrhenicum, arsenicon, borrowed from Greek arsenikón, arrhenikón, probably borrowed from Aramaic zarnīḵ "arsenic" or a cognate Semitic word, borrowed from an unattested form in a Middle Iranian language (whence Persian zarnī, zarnīk "orpiment, arsenic"), a derivative of the word for "gold" (as Manichaean Parthian zrn /zarn/ "gold," zrnyn /zarnēn/ "golden"), alluding to the yellow color of orpiment

Note: The Greek word is assumed to have been reshaped by folk-etymological association with arsenikós, arrhenikós "male, masculine." Aramaic zarnīḵ is attested in a papyrus text (an order to repair a boat) dated January, 411 b.c., found in elephantine, Egypt (see A. Cowley, Aramaic Papyri of the Fifth Century B.C., Oxford, 1923, pp. 88-97; B. Porten, The Elephantine Papyri in English: Three Millennia of Cross-Cultural Continuity and Change, Brill, 1996, pp. 115-22); the word is also attested in Syriac a number of centuries later. The Manichaean Parthian forms are from D. Durkin-Meisterernst, Dictionary of Manichaean Texts, vol. III, Part 1, Dictionary of Manichaean Middle Persian and Parthian, Brepols, 2004. Parthian zrn and zrnyn are continuations of an Old Iranian etymon represented by Avestan zarańiia- "gold"—see note at gold entry 1.

First Known Use

1747, in the meaning defined at sense 1

Kids Definition

arsenic

noun

ar·​se·​nic

ˈärs-nik, 

-ᵊn-ik

1

: a solid poisonous element that is commonly metallic steel-gray and brittle see element

2

: a white or transparent extremely poisonous oxide of arsenic used especially in insecticides

Medical Definition

arsenic

1 of 2 noun

ar·​se·​nic ˈärs-nik, -ᵊn-ik 

1

: a trivalent and pentavalent solid poisonous element that is commonly metallic steel-gray, crystalline, and brittle

—symbol As see Chemical Elements Table

2

: arsenic trioxide

arsenic

2 of 2 adjective

ar·​sen·​ic är-ˈsen-ik 

: of, relating to, or containing arsenic especially with a valence of five