The factory where steel is made — the whole site, usually enormous: furnaces, chimneys, rail lines, sometimes its own harbour. The strange thing about this word, and the thing to learn, is its grammar. It ends in s but it can be one single factory: 'there is a steelworks near the river' is correct English. And the plural looks exactly the same: 'two steelworks closed last year'. So the s tells you nothing about how many; the words around it do. This -works pattern is old and is used for several kinds of large industrial site — gasworks, ironworks, waterworks gates — and all of them behave the same way. Steelworks is more British than American; Americans more often say a steel mill or a steel plant. You meet the word in news about industry and in place names, since towns often took their name from the works that fed them.