Lead-in and Prefatory

Lead-in noun - The introductory section of a story.

Prefatory and lead-in are semantically related In some cases you can use "Prefatory" instead an adjective phrase "Lead-in".

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

Lead-in and prefatory are semantically related in introductory topic. Sometimes you can use "Lead-in" instead an adjective "Prefatory".