Prefatory and Simplex

Prefatory adjective - Coming before the main part or item usually to introduce or prepare for what follows.

Simplex and prefatory are semantically related In some cases you can use "Simplex" instead an adjective "Prefatory".

Simplex adjective - Having only one part or element.

Prefatory and simplex are semantically related in simple topic. Sometimes you can use "Prefatory" instead an adjective "Simplex", if it concerns topics such as elementary.