Here are some prefixes that sound similar and their meanings:
* "se-": This prefix often means "apart", "away", or "aside". For example:
* secede: to withdraw from an organization.
* segregate: to separate into groups.
* seize: to take hold of something forcefully.
* "semi-": This prefix means "half" or "partly". For example:
* semicircle: half a circle.
* semiannual: occurring twice a year.
* semifinal: a round of competition before the final.
If you provide more context about where you encountered the prefix "sedi", I might be able to give you a more specific answer.