opening

noun

a becoming open or causing to be open
an open place or part; hole; gap; aperture
☆ a clearing in the midst of a wooded area
1. a beginning; first part; commencement
2. start of operations; formal beginning
3. a first performance, as of a play
a favorable chance or occasion; opportunity
an unfilled position or office for which a person is wanted
Chess, Checkers the series of moves at the beginning of a game, often a specific, conventional sequence of moves

adjective

initial or introductory: opening remarks

See opening in American Heritage Dictionary 4