What's up w/ Grey's Anatomy?

Sorry if this was asked before, but why was the Grey’s Anatomy episode last sunday a repeat? I looked on a website with an episode guide and it looks as though there are four episodes left for the second season.

Typically networks don’t broadcast a show every week straight until they’re out of episodes. Almost always they stretch the episodes across the entire season, broadcasting a string of new episodes and then a few reruns. In the last few years, some shows have been broadcast without reruns in order to shorten a season when the network has agreed to buy more shows than it has room for. This happened to Alias last season and was also the way NYPD ran in some of its latter seasons.

–Cliffy

Yes, it was, Cockatiel.