This has been something that has confused me for some time. Come to find out that I’ve been using the right word all along.
Maybe you’ve assumed that discs and disks are just two different ways to spell the same thing. In a new support article, Apple Computer explains that disc refers to optical media – CDs, DVDs, etc where as disk is your computer’s hard disk or floppy disk.
So, there you go. When you need to use one of these words while writing, you’ll now know which is which.