A ballpoint pen (also eponymously known in British English and Australian English as a biro and bye-roe in Britain and Australia but sometimes /ˈbiːroʊ/ bee-roh" elsewhere, named after its credited, though contested, inventor László Bíró),'s a modern writing instrument. A ballpoint pen has an internal chamber filled with a viscous ink that's dispensed at the tip during use by the rolling action of a small metal sphere (0.7 mm to 1.2 mm in diameter) of brass, st… (More on Ballpoint)