U+70EF "烯" CJK Unified Ideograph-# Unicode Character
U+70EF "烯" CJK Unified Ideograph-# is a Chinese character (hanzi) that primarily means "alkene" or "olefin" in modern chemical terminology, representing a class of hydrocarbons containing at least one carbon-carbon double bond. Its semantic radical is "火" (fire) on the left, while the phonetic component "希" (xī) contributes to its pronunciation as "xī" in Mandarin. This character is widely used in scientific and industrial contexts in East Asia, particularly in chemistry textbooks, laboratory reports, and material science to denote unsaturated hydrocarbons such as ethylene (乙烯) and propylene (丙烯). Historically, it was coined in the early 20th century as part of a systematic effort to create Chinese characters for chemical elements and compounds, combining the fire radical with the sound "xi" to reflect the flammable nature of many alkenes.