Nineties has 6 different meanings across 2 categories:
Noun · Proper Noun
the decade from 1890 to 1899
the decade from 1990 to 1999
the time of life between 90 and 100
plural of ninety
From or evoking the 91st through 100th years of a century (chiefly the 1990s).
Alternative letter-case form of nineties, in the context of a specific decade (almost always) the 1890s or 1990s.