Mill (grinding machinery, factories, currency, and other meanings)

Grinding mills and power sources

At its core a mill is often a device for grinding or pulverizing. Traditional types include the hand-operated and stone-based mill (grinding) and the commercial gristmill used to turn grain into flour. Mechanical mills have been driven by many power sources: wind, water, animals, and human labor. Examples are the windmill, the watermill, the animal-powered horse mill, and the treadwheel (once sometimes called a "treadmill"). These devices convert natural or biological power into the rotary motion needed to operate millstones, rollers, or other processing implements.

Industrial mills and common types

From the early Industrial Revolution the term "mill" came to mean a factory or workshop where bulk processing occurred. Many early factories were situated to take advantage of water power, hence the association with mills. Common industrial uses still referred to as mills include:

• Paper mill – facilities that produce paper from pulp and other raw materials.
• Sawmill – establishments that cut logs into lumber and timber products.
• Steel mill – integrated plants that produce steel through smelting and processing.
• Sugar mill – processing of sugar cane or beets into refined products.
• Cotton mill – textile mills that card, spin, and weave cotton fibers.

Whereas "mill" once broadly meant any large factory, modern usage retains the term in specific industries and place names.

Specialized machines and technical senses

Beyond buildings and traditional grinding equipment, "mill" describes several machine types and specialized concepts. A milling machine is a tool that shapes materials by moving a workpiece against a rotating cutter. A stamp mill is a heavy, repetitive impact machine used historically in ore processing. In computing history, the analytical designs for early mechanical computers used an "arithmetical unit" sometimes called a mill, an idea appearing in Charles Babbage's notes. In finance, one obsolete but sometimes still cited usage is the mill as a fractional monetary unit equal to one-thousandth of a currency unit or one-tenth of a cent in contexts that used such subdivisions.

Other meanings, cultural uses, and idioms

The word also appears in idioms and specialized language. "Diploma mill" or "degree mill" denotes an organization that issues academic credentials with little or no legitimate study. In games, "mill" refers to a line of three pieces in Nine Men's Morris. In dance, a "windmill" or "mill" can describe a continuous rotational breakdance move. The term is also used as a company or brand name in creative industries, such as a post-production visual effects studio known simply as "The Mill."

Places, people, and continued relevance

Mill appears in place names and surnames; for example it is the name of a town in the Netherlands and forms part of many locality names near historic mill sites. In botanical citation, the abbreviation "Mill." has been used to indicate the 18th-century botanist Philip Miller. Today mills remain important as heritage sites, industrial centers, and metaphors for repeated or large-scale processing. For more specialized topics or historical details, consult resources on milling technology, industrial history, and specific mill types such as grinding mills or the watermill.

Further reading and references may be found via dedicated entries on individual mill forms and regional histories; for online summaries of particular types see curated pages on gristmills, windmills, and modern industrial sawmills. Technical discussions of milling machinery and machine tools are available under entries for milling machines and stamp mills.