I’ve noticed this particular pair getting mixed up a lot recently. In a book I was reading on butterflies (a good book, well researched and well copyedited apart from this one point), in blog posts, in things I’ve been editing … all over the place. I try not to get too annoyed by mistakes, especially common ones, but this one has been jumping out at me, so it’s obviously asking to be written about!
Something that’s discreet is careful and prudent. It fades into the shadows and doesn’t make a show of itself; it doesn’t offend.
Something that’s discrete is something that’s separate and distinct. It has specific uses in maths and science, and, although it is seen in everyday speech and writing, it might be better to just go ahead and use “distinct” instead.
Some examples: “She wore a discreet grey hat with a small feather.” “We can have an affair, but we’ll have to be discreet about it so no one finds out.” “The examination has several discrete, non-overlapping sections, all of which must be passed.”
Really, if you feel that you want to use this word, you probably want to use “discreet”.
For more troublesome pairs, choose the phrase in the category cloud to the right, or click here.