becoming open or being made open

a ceremony accompanying the start of some enterprise

the act of opening something

the first instance in which a play is publicly performed

the initial stage of the game, where players make their first moves to develop their pieces and control the center of the board

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

opportunity especially for employment or promotion