Prelusive and Prior

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

Prior and prelusive are semantically related. in preliminary topic. In some cases you can use "Prior" instead an adjective "Prelusive", when it comes to topics like introductory.

Prior adjective - Coming before all others in importance.

Prelusive and prior are semantically related. You can use "Prelusive" instead an adjective "Prior".