How to Write 羧 (suō) — Meaning “carboxyl (chemical radical)”

Picture a sheep (羊) in a chemistry lab saying "So" (sounds like suō) as it holds a flask of carboxyl acid. Another trick: the right part 夋 looks like a person running, so imagine a sheep running to add a carboxyl group to a molecule.

The left radical 羊 has three horizontal strokes; make the middle one slightly shorter and keep the whole left side narrow. The right part 夋 starts with a left-falling stroke (撇) and includes a hook — be careful not to confuse it with the similar-looking 夂 or 夊. Practice the stroke order: 羊 (6 strokes) then 夋 (7 strokes) for a total of 13.

羕 (yàng) has 永 (water) on the right and is a rare character meaning "to overflow," while 羚 (líng) has 令 on the right and means "antelope." In contrast, 羧 has 夋 on the right and is only used in chemistry. Visually, the right side of 羧 contains a hook and a vertical curve not found in 羕 or 羚.

羧 appears almost exclusively in scientific chemistry terms, such as 羧基 (carboxyl group) and 羧酸 (carboxylic acid). It is not part of everyday vocabulary and is not in the HSK list. Learning it is useful for reading Chinese organic chemistry textbooks or scientific articles.

Common words containing 羧 include: 羧基 (suō jī) — carboxyl group; 羧酸 (suō suān) — carboxylic acid; 羧化 (suō huà) — carboxylation.