A ballpoint pen (also eponymously known in British English and Australian English as a biro and pronounced /ˈbaɪroʊ/ BYE-roh in Britain and Australia but sometimes /ˈbɪəroʊ/ BEER-oh elsewhere, named after its credited, though contested, inventor László Bíró) is a modern writing instrument. A ballpoint pen has an internal chamber filled with a viscous ink that is dispensed at tip during use by the rolling action of a small metal sphere (0.7 mm to 1.2 mm in diameter) of brass, steel or tungsten carbide.

Description

There are two basic types of ball point pens: disposable and refillable.

Disposable pens are chiefly made of plastic throughout and discarded when the ink is consumed; refillable pens are metal and some plastic and tend to be much higher in price. The refill replaces the entire internal ink reservoir and ball point unit rather than actually refilling it with ink, as it takes special high-speed centrifugation to properly fill a ball point reservoir with the viscous ink. The simplest types of ball point pens have a cap to cover the tip when the pen is not in use, while others have a mechanism for retracting the tip. This mechanism is usually controlled by a button at the top and powered by a spring within the pen apparatus, but other possibilities include a pair of buttons, a screw, or a slide.

Rollerball pens combine the ballpoint design with the use of liquid ink and flow systems from fountain pens;

Space Pens, developed by Fisher in the United States, combine a more viscous than normal ballpoint pen ink with a gas pressurized piston which forces the ink toward the point. This design allows the pen to write even upside down or in zero gravity environments.

Ballpoint pens in everyday life

Ballpoint pens are ubiquitous in modern culture. While other forms of pen are available, ballpoint pens are certainly the most common and almost every household is likely to have several. The fact that they are cheaply available and convenient to use means they are often to be found on desks and also in pockets, handbags, purses, bags and in cars — almost anywhere where one could conceivably need to use a pen. Ballpoint pens are often provided free by businesses as a form of advertising — printed with a company's name, a ballpoint pen is a relatively low cost advertisement that is highly effective (customers will use, and therefore see, a pen on a daily basis). Businesses and

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