GY, Gy, or gy may refer to:
Units of measurement
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Gray (unit) (Gy), SI unit of absorbed radiation
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Giga-year, 1,000,000,000 years (non-SI)
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Galactic year, the time it takes for the Solar System to orbit the Galactic Center
Businesses and organisations
Language
People
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Pierre Gy (1924–2015), French chemist and statistician
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Garin de Gy, 14th century Catholic Master of the Order of Preachers
Places
United Kingdom
Elsewhere
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Guyana (ISO 3166: GY)
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Gy, Haute-Saône, France
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Gy, Switzerland
Science and technology
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.gy, the country code top level domain (ccTLD) for Guyana
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Mazda GY, a car engine
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Grapevine yellows, a plant disease
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Gy, the on-line charging interface in the GPRS core network