Disc or Disk: Which Is Correct?

Updated 2026-10-12 · Which One Is Correct editorial team

Quick answer: Both disc and disk are correct spellings in American English, but they are not interchangeable. Use disc for flat, round objects like optical media or body parts. Use disk for computer storage devices or any thin, circular object in technical contexts.

The Short Answer

Both are accepted spellings according to standard dictionaries. Disc is used for optical and flat round objects while disk is the usual American spelling for computer storage.

Correct Example Sentences

The laser reads data from the compact disc.
A spinal disc separates the vertebrae in your spine.
The hard disk stores all your documents and photos.
This vinyl record is a large disc made of plastic.
The artist wrote the music on a digital disk.
Please insert the disc into the player carefully.
The computer crashed after the hard disk failed.
The flat disc spins rapidly under the light.
We need to backup the disk before the update.
The new optical disc holds more movies than the old one.

Common Mistakes and Fixes

Many people mistakenly spell every round object as a disk, but a compact disc is the correct term.: Many people mistakenly spell every round object as a disk, but a compact disc is the correct term.
Using disk for a spinal disc in a medical description is an error that should be avoided.: Using disk for a spinal disc in a medical description is an error that should be avoided.
A flat round object should always be spelled with a c, not the k used for storage.: A flat round object should always be spelled with a c, not the k used for storage.
Writing disk instead of diskette for an old floppy drive component is not a mistake.: Writing diskette instead of disk for an old floppy drive component is not a mistake.
It is wrong to call a hard disk a hard disc when describing computer storage.: It is wrong to call a hard disk a hard disc when describing computer storage.
People often think disk is the only correct spelling for any circular item.: People often think disc is the correct spelling for any circular item, except for computer storage.
Spelling a computer hard drive as a hard disc contradicts standard American usage.: Spelling a computer hard drive as a hard disc contradicts standard American usage.
A spinal disc is never correctly spelled as a disk in proper medical writing.: A spinal disc is never correctly spelled as a disk in proper medical writing.
Using the letter c for computer storage instead of k is considered a spelling mistake.: Using the letter c for computer storage instead of k is considered a spelling mistake.

A Quick Test You Can Use

Ask yourself if the object is primarily related to technology or if it is a physical, round object. If it is a computer storage device, use disk. If it is an optical media item or a biological part, use disc.

Related Word Pairs

Principal vs Principle: Use principal for people or money, principle for rules.
Effect vs Affect: Use affect as a verb meaning to influence, effect as a noun meaning result.
Compliment vs Complement: Use compliment to praise, complement to complete or enhance.
Stationary vs Stationery: Use stationary for not moving, stationery for writing paper.
Their vs There vs They're: Use their for possession, there for place, they're for they are.

Frequently Asked Questions

When should I use disc versus disk?

Use disc for flat round objects like optical media or body parts. Use disk for computer storage devices or general technical contexts where thin circular shapes are implied.

Are both spellings accepted in formal writing?

Yes, both spellings are accepted by major dictionaries. However, you must choose the correct one based on the specific meaning and object you are describing in your sentence.

What is the difference between hard disk and hard drive?

Hard disk and hard drive refer to the same computer storage device. The term hard disk is more common in American English while hard drive is often used globally.

Does British English change these spellings?

British English often prefers the letter c in both cases, so it may use disc for both computer storage and optical media. Always follow the style guide of your publication.