A recent Baltimore Sun article contained a sentence saying that federal proceedings supercede local judgments. So they do, but the word is supersede.
Supersede derives from the Latin supersedere: super (above) sedere (to sit). To supersede is, from the literal roots of the word, to be superior to, to sit above.
Merriam-Webster says that the spelling supercede has turned up regularly since the 17th century (so much for any expectation that it would have been rare when everyone studied Latin) but is widely considered an error. It is probably a matter of time until it is widely listed in dictionaries as an acceptable variant.
While we are thinking about Latin, a reminder that this is graduation season. You who cross the platform to receive the diploma and the handshake will be an alumnus or an alumna, collectively alumni or, in some cases, alumnae. Arnold Zwicky, having come across a Web site in which a man describes himself as “a Distinguished Alumnae,” will sort out the terms for you.
If you want to appear edumacated, you will not say, “I am an alumni,” and you will not spell supersede with a c.