is a specific kind of: period, period of time, time period.

is a broader term that covers: 1900s | 1530s | 1920s, twenties | 1820s | 1930s, thirties | 1830s | 1940s, forties | 1840s | 1950s, fifties | 1850s | 1750s | 1960s, sixties | 1860s | 1760s | 1970s, seventies | 1870s | 1770s | 1980s, eighties | 1880s, eighties | 1780s | 1990s, nineties | 1890s, nineties | 1790s ... show more.

has as a part: twelvemonth, year, yr.

is a part of: century.