The question of whether to use disc or disk can be a bit circular: in some cases, one is definitely preferred, but in many cases their use overlaps—meaning they’re often interchangeable. This is because both words typically refer to something round and flat (though not always, as we’ll see). The difference, when there is one, usually just depends on what the established preference is.
The discrepancies can be disconcerting, but we hope this discussion will help you discard any confusion or discontent.
⚡ Quick summary
Disc and disk can be and are used interchangeably in many contexts, though disk may be slightly more common. The D in CD and DJ (usually) stands for disc, which is the spelling also used in disc golf. The spelling disk is usually used in the context of computer storage in terms like disk drive, floppy disk, and hard disk. It’s also usually used when referring to intervertebral disks—the ones in the spine.
Should I use disc or disk?
In most cases, disc and disk can be—and are—used interchangeably. In general, the word disk was once much more commonly used, but the two words now have a relatively similar level of use.
This all means that there’s really no good rule to remember when to spell it one way or the other. Instead, here’s a handy list showing which spelling is more commonly used in a specific term or a particular context.
disc golf
The various types of flat, plastic circles that are thrown in various games (including disc golf) can all be called discs. The type of flying disc used for a casual toss—and in the sport known as Ultimate—is popularly known by the brand name Frisbee.
compact disc, disc jockey
In the context of music, the D in CD and DJ most often stands for disc—though you may see disk used in some cases. And, technically speaking, a musical compact disc can be considered a type of compact disk, the broader name for any 4.75-in (12-cm) optical disk (which, yes, can also be called an optical disc).
disk drive, disk space, hard disk, magnetic disk, floppy disk
In the context of computer data storage, the spelling is usually disk.
Anyone just now discovering what a floppy disk is might be wondering why it’s called a disk when it’s square rather than round, but it’s because the actual disk inside the plastic shell is actually round. You can remember to use the spelling with a k in this context because floppy disks are sometimes called diskettes (not “discettes”).
slipped disk, herniated disk
The pads between the spinal vertebrae are usually called disks or intervertebral disks.
flat, circular objects
In general, any thin, flat, circular plate or object—or one that at least appears to be round and flat—can be referred to as a disk or a disc. While the spelling disc is very common in general, the spelling disk is probably even more common, especially in several specific contexts.
astronomy
Surfaces of heavenly bodies appear flat during regular observation, and for this reason they are often referred to as disks, as in the disk of the moon and the solar disk.
biology
Roundish, flat structures in a body can be called disks, as in blood disk (also called a platelet) and germinal disk (also called a blastodisk).
geometry
The domain bounded by a circle can be called the disk.
plants and flowers
The central portion of the flowerhead is called the disk.
Examples of disc and disk used in a sentence
That was a lot of info! Let’s see some examples of these senses in use.
- The mysterious disc in the video—purported to be an extraterrestrial craft—turned out to be a Frisbee.
- Growing up, I always wanted to be a radio disc jockey, but that’s only because podcasters didn’t exist yet.
- The telescope is set up to observe the disk of the moon.
- I want to copy the contents of the floppy disk to the hard disk—is that possible?
- How much disk space is available?
- She’s been out of work with a herniated disk.
