Opening

an open or empty space in or between things

a ceremony accompanying the start of some enterprise

becoming open or being made open

the first performance (as of a theatrical production)

the act of opening something

opportunity especially for employment or promotion

the initial part of the introduction

a possible alternative

an aperture or hole that opens into a bodily cavity

a vacant or unobstructed space that is man-made

an entrance equipped with a hatch

a recognized sequence of moves at the beginning of a game of chess

the first of a series of actions

first or beginning