extended has 7 distinct synonyms spread across 3 of its 5 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 unextended.
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.
relatively long in duration; tediously protracted
“a drawn-out argument”
fully extended or stretched forth
“an extended telescope”
drawn out or made longer spatially
“Picasso's elongated Don Quixote”
large in spatial extent or range or scope or quantity
“an extensive Roman settlement in northwest England”
1 of the 5 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for extended.
Synonyms, antonyms and the broader and narrower relations for extended come from Princeton University’s WordNet. Full sources and licences.