A ballpoint pen (Philippine English: ballpen, British English: biro) is a writing instrument, with an internal ink reservoir and a sphere for a point. The internal chamber is filled with a viscous ink that is dispensed at its tip during use by the rolling action of a small sphere. The sphere, usually from 0.5 mm to 1.2 mm in diameter, may be made of brass, steel, tungsten carbide, or any durable, hard (nondeformable) material.
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“Words are but air; the pen leaves a mark.”
—Chinese proverb.