fertility has 8 distinct synonyms spread across 3 of its 3 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 infertility.
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 ratio of live births in an area to the population of that area; expressed per 1000 population per year
the state of being fertile; capable of producing offspring
the property of producing abundantly and sustaining vigorous and luxuriant growth
“he praised the richness of the soil”
Synonyms, antonyms and the broader and narrower relations for fertility come from Princeton University’s WordNet. Full sources and licences.