Super

There's a small handful of words in English that end in "-cede"; accede, intercede, precede, and a few more. There are three that end in "-ceed": succeed, proceed, and exceed. But only one ends in "-sede".

If I were learning English from scratch, I'd be railing against such nonsensical spelling rules. All these words have the same sound: why can't they all have the same spelling?

Let's blame Latin. It isn't going to complain. All the "-cede" words come from the same root, "cedere", to go. Intercede: to go between. Precede: to go before. All the "-ceed" words come from...well, the same root, unfortunately. Their spelling is a mere accident of history: it would have been nice if their spellings had been standardized to match the others, but they've been cemented in place by centuries of usage. (All the "-ceed" words had alternate spellings of "-cede", and with a few variations such as "ceede" for "cede", the reverse is also true.)

The one holdout, "supersede", comes from an altogether different source: "sedere", "to sit". (The word "sedate" comes from a related meaning of "sedere": "to settle".) To supersede is to literally sit above something; its current meaning is almost metaphorical, but the sense is still there.

And this is why I get ticked off when I see the spelling "supercede". It's understandable, but it's also wrong.