generation has 5 distinct synonyms spread across 3 of its 7 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.
all the people living at the same time or of approximately the same age
group of genetically related organisms constituting a single step in the line of descent
Synonyms, antonyms and the broader and narrower relations for generation come from Princeton University’s WordNet. Full sources and licences.
the normal time between successive generations
“they had to wait a generation for that prejudice to fade”
a stage of technological development or innovation
“the third generation of computers”
the production of heat or electricity
“dams were built for the generation of electricity”
the act of producing offspring or multiplying by such production