Prepared mustard in a recipe refers to any type of mustard that is already made, according to the French's Food Company. Recipes use this term to distinguish prepared mustard from dry mustard, which is sold as a spice.
A prepared mustard includes mustard seeds, vinegar and spices, and it is about half the strength of dry mustard. A recipe that calls for prepared mustard usually specifies what type or flavor. Possible choices include Dijon mustard, sweet mustard and yellow mustard, among other varieties specific to geographic regions. Yellow mustard is also referred to as American mustard. The mild flavor of yellow mustard makes it an appropriate choice if the recipe does not specify what type to use.