Astraeus hygrometricus, commonly known as the Hygroscopic Earthstar
Hydroscopic OR Hygroscopic!
Which one means: Attracts water?
Your spell-checker will not help you out this time.
Glycerin soap is desirable because, those of us who use soaps rich in glycerin, are seeking a way to hydrate the skin after we bathe.
For this reason people say that glycerin is hygroscopic. Spoken, we might think they said hydro- because we are used to that word combined with something to do with water (hydroplane, hydroelectric, hydrotherapy, hydroponic). There is a device for taking pictures underwater called a hydroscope, hence the correct spelling of the word hydroscopic.
Glycerin-rich soaps are HYGROSCOPIC. I, myself have made the error of using the prefix, “hydro-” when talking and writing.
So, both words are REAL but only one means, “attracts water”. Let’s hope no one who makes those standardized tests for schools finds out about this one!