I realize that. If you read the novelizations, they might say Sith. I have an unopened Darth Vader keychain whose package says Dark Lord of the Sith. But the original movies don't say Sith. (I don't recall the specifics of the radio dramas.) They just refer to the Dark Side of the Force. Just like Return of the Jedi doesn't speak the word Ewok, but everyone knows what they are through the end credits and merchandise.There's a 1997 Star Wars video game set years after Return of the Jedi in which the player fights seven Dark Jedi, but that's all they're ever called, never Sith. The Sith aren't mentioned until the player goes to Korriban, the Sith homeworld. You can be a Dark Jedi just by doing evil things with Force powers. It takes special disciplines and beliefs to follow Sith ways. Star Wars doesnt' mention "Star Destroyers", just Imperial Cruisers Leia points at the Executor when escaping Bespin and says "Star Destroyer..."