introductory vs opening

introductory is not a noun while opening is a noun.

Word	Noun	Adjective	Verb	Adverb
introductory	No	Yes	No	No
opening	Yes	Yes	No	No

introductory (noun)	opening (noun)
	a recognized sequence of moves at the beginning of a game of chess
	the act of opening something
	becoming open or being made open
	the first of a series of actions
	a vacant or unobstructed space that is man-made
	an entrance equipped with a hatch; especially a passageway between decks of a ship
	an aperture or hole that opens into a bodily cavity
	a possible alternative
	the initial part of the introduction
	the first performance (as of a theatrical production)
	a ceremony accompanying the start of some enterprise
	an open or empty space in or between things
	opportunity especially for employment or promotion

introductory (adjective)	opening (adjective)
serving as a base or starting point	first or beginning
serving to open or begin
serving as an introduction or preface