Sterols are a group of organic molecules found in all living organisms. They play a vital role in maintaining the structure and fluidity of biological membranes and serve as precursors for the biosynthesis of hormones, bile acids, and vitamin D. Some common synonyms for the word 'sterol' include steroid alcohols, steroid ketones, sterol esters, and sterol glycosides. Other related terms include ergosterol, a type of sterol found in fungi, and phytosterols, which are naturally occurring plant compounds that have a similar structure to sterols. In addition, there are numerous synthetic sterol analogs that have been developed for medicinal and biotechnological applications, such as cholesterol-lowering drugs.