The watery part of milk that separates from the curds, as in the process of making cheese.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "whey" in a sentence
"If I forget to feed it for several weeks, it will separate and the whey is a not very attractive grey liquid but it still works once fed and I haven't killed it yet."
"It starts out the same way as any other yogurt, with milk and an active yogurt culture, but before packaging the yogurt is strained to remove some the the excess whey from the yogurt and make it thicker."
"Earlier attempts to make ethanol from waste weren't practical because the waste, whey, is a highly-sought commodity due to its protein -- a popular additive in both human and animal food products."