beginning has 13 distinct synonyms spread across 4 of its 6 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 3 recorded opposites are ending, middle, end.
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.
the event consisting of the start of something
“the beginning of the war”
the place where something begins, where it springs into being
“the Italian beginning of the Renaissance”
the act of starting something
“he was responsible for the beginning of negotiations”
Synonyms, antonyms and the broader and narrower relations for beginning come from Princeton University’s WordNet. Full sources and licences.