preliminary
Another word for a document's introductory text is "preface" or "foreword."
No the word introductory is not a noun. It is an adjective.
There are 4 syllables in the word introductory.
happenAlso occur or two words ...will be
An introductory word of an adjective clause is a word that introduces the clause and provides context for the noun it is modifying. Common introductory words include who, which, that, whose, whom, where, and when.
Event
Another word for strange event or equation
another word for terrible
trigger event
Incident.
awesome
perhaps event is the word you are looking for.