arrangement has 8 distinct synonyms spread across 5 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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 thing arranged or agreed to
“they made arrangements to meet in Chicago”
an orderly grouping (of things or persons) considered as a unit; the result of arranging
“a flower arrangement”
an organized structure for arranging or classifying
“he changed the arrangement of the topics”
the spatial property of the way in which something is placed
“the arrangement of the furniture”
a piece of music that has been adapted for performance by a particular set of voices or instruments
the act of arranging and adapting a piece of music
Synonyms, antonyms and the broader and narrower relations for arrangement come from Princeton University’s WordNet. Full sources and licences.