gray / grey are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
gray: (noun) a neutral achromatic color midway between white and black. (noun) the SI unit of energy absorbed from ionizing radiation; equal to the absorption of one joule of radiation energy by one kilogram of matter; one gray equals 100 rad. (noun) English radiobiologist in whose honor the gray (the SI unit of energy for the absorbed dose of radiation) was named (1905-1965). (noun) English poet best known for his elegy written in a country churchyard (1716-1771). (noun) American navigator who twice circumnavigated the globe and who discovered the Columbia River (1755-1806). (noun) United States botanist who specialized in North American flora and who was an early supporter of Darwin's theories of evolution (1810-1888).
grey: (noun) United States writer of western adventure novels (1875-1939). (noun) Queen of England for nine days in 1553; she was quickly replaced by Mary Tudor and beheaded for treason (1537-1554). (noun) Englishman who as Prime Minister implemented social reforms including the abolition of slavery throughout the British Empire (1764-1845). (noun) any organization or party whose uniforms or badges are grey. (noun) clothing that is a grey color. (noun) horse of a light gray or whitish color. (verb) make grey. (verb) turn grey. (adjective) of an achromatic color of any lightness intermediate between the extremes of white and black. (adjective) showing characteristics of age, especially having grey or white hair; -Coleridge. (adjective) used to signify the Confederate forces in the American Civil War (who wore grey uniforms). (adjective) intermediate in character or position.
gray: g·r·EY
grey: g·r·EY
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)