Q: My dictionary says “disk” and “disc” are simply variant spellings of the same word. But I’ve run across a technical article from Apple that asserts “disc” refers to optical media while “disk” refers to magnetic media. Have you ever heard of this distinction?
A: It’s true that “disc” is a variant spelling of “disk,” but Apple is technically right. Each spelling has marked out its own territory in the technological wilderness, though many non-techies seem to be unaware of the distinction.
As Apple’s support site says, discs are “optical media, such as an audio CD, CD-ROM, DVD-ROM, DVD-RAM, or DVD-Video disc,” while disks are “magnetic media, such as a floppy disk, the disk in your computer’s hard drive, an external hard drive.”
If you’re like us, you may find the optical-vs.-magnetic distinction hard to remember. When in doubt, we go to a dictionary or usage guide. The New York Times Manual of Style and Usage has a helpful entry:
“Use disc in references to phonograph records (disc jockey, discography), optical and laser-based devices (compact disc, laser disc, videodisc), farm implements (disc harrow), and brakes (disc brakes). Use disk in references to the magnetic storage devices used with computers (floppy disk, hard disk) and to the fiber and cartilage between the vertebrae (slipped disk).”
In ordinary usage, as we mentioned, many people don’t follow the distinctions found in dictionaries, style manuals, and technical articles.
Experts do prefer “disc jockey” to “disk jockey,” and a comparison with Google’s Ngram viewer shows that “disc jockey” is considerably more popular than “disk jockey” in published books.
The word was spelled “disk” when it entered English in 1665 and referred to either the discus that athletes throw or the flat, circular form of a celestial object like the sun or moon. It’s ultimately derived from the Latin discus and the Greek δίσκος (diskos).
Standard dictionaries, like American Heritage and Merriam-Webster, generally say “disc” is a variant spelling of “disk.” The Oxford English Dictionary, an etymological reference, gives “disk” as a variant of “disc.”
The OED, under its entry for “disc, disk,” adds that “disc is now the more usual form in British English,” except in the computing sense, “where disk is commoner as a result of US influence.”
Merriam-Webster’s Collegiate Dictionary (11th ed.) has this as one definition of “disk”: “a round flat plate coated with a magnetic substance on which data for a computer is stored.” But it says that an “optical disk” (like a “videodisc” or a “CD”) is usually spelled “disc.”
And The American Heritage Dictionary of the English Language (4th ed.), under its entry for “compact disk,” has an extensive usage note that we’ll quote in its entirety (we’ll add paragraphing to make it easier to read):
“When new words come into the language, they often have different forms for a period until one form wins out over the others. There are occasions when competing forms remain in use for a long time. The word disk and its descendant compound compact disk represent good examples of this phenomenon.
“Disk came into English in the mid-17th century and was originally spelled with a k on the model of older words such as whisk. The c-spelling arose a half century later as a learned spelling derived from the word’s Latin source discus. Both disc and disk were used interchangeably into the 20th century, with people in Britain tending to use disc more often, and Americans preferring disk.
“The spellings also began to be sorted out by function. Late in the 19th century, for reasons that are not clear, people used disc to refer to the new method of making phonograph recordings on a flat plate (as opposed to Edison’s cylindrical drum). In any case, the c-spelling became conventional for this sense, which is why we listen to disc jockeys and not disk jockeys.
“In the 1940s, however, when American computer scientists needed a term to refer to their flat storage devices, they chose the spelling disk, and this became conventionalized in such compounds as hard disk and floppy disk. When the new storage technology of the compact disk arose in the 1970s, both c– and k-spellings competed for an initial period. Computer specialists preferred the familiar k-spelling, while people in the music industry, who saw the shiny circular plates as another form of phonograph record, referred to them as compact discs.
“These tendencies soon became established practice in the different industries. This is why we buy compact disks in computer stores but get the same storage devices with different data as compact discs in music stores. Similarly, the computer industry created the optical disk, the format that the entertainment industry used to create the videodisc.”
[Note: This post was updated on March 9, 2022.]