noun
the 1900s
Refers to the decade from 1900 to 1909, or sometimes loosely to the entire 20th century. Context usually clarifies the intended range.
千九百年代の初めに、多くの国で産業が急速に発展した。
In the early 1900s, industry developed rapidly in many countries.
この写真は千九百年代のファッションをよく表している。
This photo captures the fashion of the 1900s well.
Compound of 千 (thousand), 九 (nine), 百 (hundred), 年 (year), and 代 (era/decade). Literally 'the thousand-nine-hundred-years era'.