Lipoids

Part of speech: noun

Definitions

1. Naturally occurring fatty or oily organic substances that are insoluble in water and include fats, waxes and steroids
2. Oily or fat-like organic molecules found in living tissue, insoluble in water but soluble in solvents such as ether
3. A class of greasy biological compounds, including fats, waxes and sterols, that make up cell membranes and store energy

Etymology: "Lipoids" is simply the plural of "lipoid," a noun for fat-like substances, and it is built from two pieces. The first, "lip-," comes from the Greek "lipos," meaning fat, the same root that gives English words such as "lipid." The second, "-oid," comes from Greek "-oeidēs," meaning "resembling" or "having the form of," so a lipoid is something that resembles fat without being fat itself. The construction is a plain technical coinage rather than an old folk word, so there is no ancient usage to recover. Chemists and biologists formed it from classical building blocks to name a broad class of substances that share fat-like properties, such as dissolving in oils and not in water, while differing in chemical structure. The plural form, "lipoids," simply counts more than one of these substances.

Synonyms: lipids, fats