An ESL speaker asks for a discussion of the nouns factory, industry, and plant in the context of the following: “mineral water factory,” “mineral water industry,” and “mineral water plant.”
factory
An earlier meaning of factory was “the employment, office, or position of a factor.” A factor, as in the word cornfactor, is “an agent who buys and sells, or transacts other business, on behalf of another person or company.”
In the context of manufacturing, a factory is “a building or range of buildings for the manufacture or assembly of goods or for the processing of substances or materials.” The earliest OED citation of this meaning of factory (1618) refers to a facility for the printing and manufacture of books.
industry
The noun industry has several meanings. The relevant definition in this discussion is this one:
A particular form or sector of productive work, trade, or manufacture. In later use also more generally: any commercial activity or enterprise. Also with modifying word indicating the type of activity or principal product: banking industry, car industry, film industry, heavy industry, service industry, tourist industry, etc.
plant
The noun plant has numerous meanings, but in the context of manufacturing, plant is often a synonym for factory:
the premises, fittings, and equipment of a business; a factory, a place where an industrial process is carried out. In extended use: the workers employed at a business, institution, or factory.
“A mineral water factory” can describe a place “for the processing of mineral water.” Perhaps more commonly, such a facility is called “a bottling plant.”
The phrase “mineral water industry” connotes all the commercial activity that goes into the acquisition, preparation, and sale of mineral water.
‘Plant’ can also mean the machinery used in factories. If ‘factory’ and ‘plant’ are both used in the same piece of writing it might indictate they have different meanings.