“Script” is the most general of the three terms, and is not reserved for any specific type of media. “Screenplay” specifically refers to the script of a film or television program. “Teleplay” is even more specific, and is only used when referencing television scripts.
So a teleplay is a type of screenplay which is a type of a script.
Since “script” is such a general term, script formatting can vary wildly. All screenplays share a general universal format, but there can be slight variations based on type or other factors. Multicamera teleplays, for instance, have double-spaced dialogue, while single-camera teleplays and film screenplays do not.
* [Script, story, screenplay](http://johnaugust.com/2003/script-story-screenplay “Script, story, screenplay”)
* [Television scripts vs. Screenplays](http://johnaugust.com/2003/television-scripts-vs-screenplays “Television scripts vs Screenplays”)
* [Specs, treatments and pitches](http://johnaugust.com/2003/specs-treatments-and-pitches “Specs, treatments and pitches”)