opening has 13 distinct synonyms spread across 7 of its 14 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is closing.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a ceremony accompanying the start of some enterprise
becoming open or being made open
“the opening of his arms was the sign I was waiting for”
the first performance (as of a theatrical production)
“the opening received good critical reviews”
opportunity especially for employment or promotion
“there is an opening in the sales department”
the initial part of the introduction
“the opening established the basic theme”
an aperture or hole that opens into a bodily cavity
“the orifice into the aorta from the lower left chamber of the heart”
an entrance equipped with a hatch; especially a passageway between decks of a ship
a recognized sequence of moves at the beginning of a game of chess
“he memorized all the important chess openings”
first or beginning
“the memorable opening bars of Beethoven's Fifth”
Synonyms, antonyms and the broader and narrower relations for opening come from Princeton University’s WordNet. Full sources and licences.