Alum

Part of speech: noun

Pronunciation: /ˈæl.əm/

Definitions

1. A chemical substance that consists of a hydrated double sulfate and is commonly found in water treatment, culinary applications, and as an ingredient in cosmetics
2. This compound appears in various forms and serves purposes in purifying water, enhancing flavor in foods, and being a part of some personal care products
3. A crystalline chemical compound made of double sulfates that has uses in water purification, cooking, and cosmetics

Etymology: Alum is one of those rare English words that is really two unrelated words sharing a sound. The mineral sense comes from Latin "alūmen," which meant the same astringent salt, and it reached English through Anglo-Norman "alum" or "alun" before appearing in Middle English as "alym," "alyme," or "alum." The Latin word itself is tied to the idea of bitterness and sharpness, which suits a substance prized for drawing and tightening. The other alum has nothing to do with chemistry. It is a clipping of "alumnus" and "alumna," the Latin words for a foster child or pupil, from the verb "alere," to nourish. English speakers dropped the gendered Latin endings, "-us" and "-a," and kept the stem, so a graduate of a school or college became an "alum." Both words arrived in English from Latin, but one came in as a bitter salt and the other as a student.

Synonyms: potassium aluminum sulfate