sulfur

noun

sul·​fur ˈsəl-fər 

variants or chiefly British sulphur

: a nonmetallic chemical element that is an essential element for all life, resembles oxygen in chemical properties, and is used especially in the form of sulfuric acid to extract phosphates from ores see Chemical Elements Table

sulfury adjective

or chiefly British sulphury

ˈsəl-fər-ē 

Is it sulfur or sulphur?: Usage Guide

The spelling sulfur predominates in U.S. technical usage, while both sulfur and sulphur are common in general usage. British usage tends to favor sulphur for all applications. The same pattern is seen in most of the words derived from sulfur.

Examples of sulfur in a Sentence

Recent Examples on the Web

In a study conducted on mice, scientists from the Massachusetts Institute of Technology (MIT) found that cysteine, a sulfur-containing amino acid, had the strongest rejuvenating effect on stem cells and early-stage intestinal cells, which are often damaged during radiation therapy for cancer. —Deirdre Bardolf, FOXNews.com, 16 Oct. 2025

However, the analysis showed that compared to the ratios of different isotopes of sulfur on Earth, the moon seems to be depleted in sulfur-33 (meaning sulfur with 33 neutrons), which is one of the four stable sulfur isotopes (sulfur-32, sulfur-34 and sulfur-36 being the others). —Keith Cooper, Space.com, 13 Oct. 2025

The Two-Stage Tear Cascade While past research had already identified the irritant in onions—known to chemists as propanethial S-oxide—this study is the first to explain how the sulfur compound reaches a cook's eyes. —Maria Morava, MSNBC Newsweek, 8 Oct. 2025

Researchers have long assumed that sulfur isotopes would likely also exhibit these similarities. —Chris Young, Interesting Engineering, 7 Oct. 2025

Word History

Etymology

Middle English sulphur brimstone, from Latin sulpur, sulphur, sulfur

First Known Use

14th century, in the meaning defined above

Phrases Containing sulfur

• sulfur bacterium
• sulfur dioxide
• sulfur mushroom
• sulfur polypore
• sulfur shelf

Rhymes for sulfur

• sulphur

Kids Definition

sulfur

noun

sul·​fur

variants also sulphur

ˈsəl-fər 

: a nonmetallic element that occurs either free or combined especially in sulfides and sulfates, is found in proteins, exists in several forms including yellow crystals, and is used especially in the chemical and paper industries, in strengthening rubber, and in medicine for treating skin diseases see element

Medical Definition

sulfur

1 of 2 noun

sul·​fur

variants or chiefly British sulphur

ˈsəl-fər 

: a nonmetallic element that occurs either free or combined especially in sulfides and sulfates, is a constituent of proteins, exists in several allotropic forms including yellow orthorhombic crystals, resembles oxygen chemically but is less active and more acidic, and is used especially in the chemical and paper industries, in rubber vulcanization, and in medicine for treating skin diseases

—symbol S see Chemical Elements Table

sulfur

2 of 2 adjective

variants or chiefly British sulphur

: of, relating to, or resembling sulfur : containing or impregnated with sulfur