linear has 6 distinct synonyms spread across 5 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 3 recorded opposites are nonlinear, planar, cubic.
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.
of or in or along or relating to a line; involving or having a single dimension
“a linear measurement”
Synonyms, antonyms and the broader and narrower relations for linear come from Princeton University’s WordNet. Full sources and licences.
(of a leaf shape) long and narrow