Gray as noun:
Gray as adjective:
Gray is used to describe nouns that are intermediate between black and white. The gray area. It is also used to define a cloudy, stormy and dull weather. Gray is sometimes used to refer to the elderly people or people of old age. He’s getting gray or Gray Power. Gray is often implied to describe the illness or dull mood of a person.
Gray as verb:
Now that you know the meaning of the word, which gray should you use? The simple answer to that is any. Both of the spellings of gray have emerged from the Old English word gr.g, and many spellings have been evolved which can be seen in the old literature. By eighteenth century, grey was the common spellings adopted by most of the people. Later, Samuel Johnson, a legendary lexicographer suggested gray was a better option, so in nineteenth century most of the English dictionaries prescribed gray. The dispute went on and twentieth century again accepted grey as the right spellings everywhere except the United States.
Grey with an e is the right spellings all the world except America. So if you belong to any other English speaking community but America be it Europe, Australia or anywhere else, you should use an e while writing grey.
Are Gray and Grey always interchangeable?
In common usage there really is no difference between the two. Gray area/grey area both represent an area with different characteristics, graybeard/greybeard both represent an elderly man with a beard, and gray squirrel/grey squirrel both represent a squirrel found in Atlantic. Although, if you are an artist and come across color swatches, it is possible that both spellings of gray may refer to different (light and dark) shades of gray. More importantly, some cases need careful mindedness of the vowel used for writing gray, like a greyhound (a breed of dogs) is always written with e whereas grayling (a species of fish) is always written with an a. If a person’s last name is Grey, then you have no right to write it Gray which means that proper nouns are off limits.