Original: The one-volume Propædia is the first of three parts of the 15th edition of Encyclopædia Britannica, the other two being the 12-volume Micropædia and the 17-volume Macropædia.
Simplified: The Propædia is the first of three parts of the Encyclopaedia Britannica,, the other two being the 12-volume Micropædia and the 17-volume Macropædia.