R4, R04, R.4, R-4, or R/4 may refer to:

Military

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Aircraft

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  • Caudron R.4, World War I French reconnaissance aircraft, first flown in 1915
  • Curtiss R-4, air ambulance version of the American Curtiss Model R utility aircraft, first flown in 1915
  • Sikorsky R-4, American helicopter, first flown in 1942

Ships

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Weapons

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Other military

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  • Plan R 4, the World War II British plan for an invasion of the neutral state of Norway in April 1940

Science

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  • R4, designation of risk phrase "Forms very sensitive explosive metallic compounds"
  • R4 nuclear reactor, the fourth nuclear reactor built in Sweden
  • Exotic R4, in mathematics, a differentiable manifold

Transportation

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Cars

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Roads

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Other transportation

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Video games

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Other uses

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See also

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