People may not burn their favorite music onto Compact Discs anymore, but one thing’s for sure: discs will always be a thing. But how is it supposed to be spelled?  Is it “disc” or “disk”? A “disc” can be any round, flat object. But…so can a “disk”. So, how exactly are you supposed to know when to use disc over disk?

There’s no real convenient origin story as to the distinction between the two forms: both come from the Latin “discus” (which, in Greek, is spelled “diskos”). The oldest known English language references date back to the mid-1600s, with the word being spelled with a k, which most lexicologists attribute to the already-set precedents of other similar words that end with -isk (“frisk”, “whisk”, etc.). But by the 1700s, some folks started using disc instead thanks to the influence of the word’s Latin predecessor. For the next few centuries, the only thing that might’ve determined with any sort of consistency how you wrote it, disc or disk, was where you lived: Americans favored the version with a “k”, while the UK preferred to end theirs with a “c”. But even that rule-of-thumb wasn’t set-in-stone.

Nowadays, it’s still a toss-up between disc & disk, no matter what you’re talking about. For instance, the Mayo Clinic refers to ruptured vertebrae as herniated disks (using the k form of the word), while the American Association of Neurological Surgeons calls them herniated discs. In certain cases, though, one spelling can be so common that the other is usually considered incorrect. A perfect example is the music industry’s use of the compact disc, with the c form of the word having been the norm since round records came to prominence in the late 1800s (not to mention the disc jockeys who spin those discs). Also, the correct way to describe a Frisbee is as a flying disc. But then, there’s the floppy disk, the magnetic computer component created by software engineers, for which the k form not only took hold for the square disks, themselves, but also the disk drives into which they’re inserted.

There’s no clear logic explaining those usages, they were all pretty much just spelling trends that caught on. So, it isn’t always easy to know which items might be discs & which might be disks. But Merriam-Webster does offer a helpful tip to help you out: compact discs (and flying ones) are round, just like the letter c. Floppy disks are all about lines & edges, just like the letter k.

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