You know that color you get when you mix black and white? How do you spell it? People seem to have trouble with it—at least, that’s what the sea of online content explaining the issue would have us believe. However, if you were to look up a list of commonly misspelled words in the English language, you probably wouldn’t find “gray” or “grey” among them. The reason, of course, is simple: both spellings of the word are correct.
Gray is a word we can use as a noun, an adjective, and an adverb. As a noun, gray refers to any of the neutral colors between black and white. If we were to use it in a sentence, we would say:
The wall was painted a light shade of gray.
As an adjective, gray can be used to describe something that is of a gray color. It can also be used to describe something that’s dull, joyless, or ambiguous:
The gray dog was walking down the street.
Paula was having a gray day.
The business operated in a legal gray area.
We use gray as a verb when we want to say that something is becoming gray. Because gray hair is usually associated with aging, we sometimes mention it as a way to show that someone is getting older:
John’s hair started to gray long before he retired.
Both gray and grey come from the Old English word grǽg. Over time, many different spellings of the word developed. The Middle English poem “The Owl and the Nightingale,” which was written in the twelfth or thirteenth century, uses the spelling “greie.” The fourteenth-century translation of the French poem “Roman de la Rose” uses the spelling “greye.” “Graye” can be found in the poem “Piers Plowman” written by William Langland in the second half of the fourteenth century. Examples of the spellings we use today can also be found in Middle English literature.
By the eighteenth century, “grey” had become the more common spelling, even though the legendary lexicographer Samuel Johnson thought that “gray” was a better version. In the nineteenth century, English dictionaries followed Johnson’s cue and prescribed “gray” as the correct version, but to no avail. By the twentieth century, “grey” had become the accepted spelling everywhere except in the United States.
And that’s how things stand today: “gray” is the preferred spelling in the United States, while “grey” is used everywhere else. So, if you’re American, you’ll write “gray,” and if you’re English, you’ll write “grey.” You can see the difference if you closely observe British and American media:
BBC: At the time, he was wearing a grey suit jacket, dark trousers, a light blue shirt and blue tie.
Huffington Post: Gray Hair. It will arrive for most of us at some point in our lives.
While you could probably use “grey” in the US and “gray” in the UK with no problems, the two are not always interchangeable. With proper nouns, the spelling isn’t flexible. Grey’s Anatomy is a TV show about a character named Meredith Grey. Gray’s Anatomy is an influential anatomy handbook written by Henry Gray. Greyhound is a breed of dog, and it’s always spelled with an “e.” One gray is a unit that’s used to measure the amount of ionizing radiation absorbed per kilogram of matter. But in all other cases, remember: E is for England, A is for America.
from Grammarly Blog https://www.grammarly.com/blog/which-is-correct-gray-or-grey/