Partial conversion

A partial conversion is a PWAD that replaces a portion of the resources of the original game's IWAD. In contrast to a total conversion, the partial retains enough visuals, sounds, and gameplay mechanics to be considered a variant of the original, not a separate game.

There is no formal criteria for what should be considered a partial conversion. The term is believed to have been coined by the STRAIN project, since its scope of changes to Doom were less than existing total conversions, like Aliens TC.