structure has 9 distinct synonyms spread across 3 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 manner of construction of something and the arrangement of its parts
“artists must study the structure of the human body”
the complex composition of knowledge as elements and their combinations
“his lectures have no structure”
a particular complex anatomical part of a living thing and its construction and arrangement
“he has good bone structure”
the people in a society considered as a system organized by a characteristic pattern of relationships
“the social organization of England and America is very different”
give a structure to
“I need to structure my days”
Synonyms, antonyms and the broader and narrower relations for structure come from Princeton University’s WordNet. Full sources and licences.