Open English Wordnet
Nouns
(n)birthrate, birth rate, fertility, fertility rate, natalitythe ratio of live births in an area to the population of that area; expressed per 1000 population per year
(n)richness, rankness, prolificacy, fertilitythe property of producing abundantly and sustaining vigorous and luxuriant growth“he praised the richness of the soil”, “weeds lovely in their rankness”