(n) The century that began on January 1, 1900, and finished on December 31, 1999. About equal to the twentieth century.
(n) The decade that started on January 1, 1900 and ended on December 31, 1909. The noughties.
(n) the ten years from 1900 to 1909
1900s in Community Dictionary
the time scale that began on January first 1900 and finished December 31st 1999. Frequently confused with the 20th century (which began and finished precisely 1 year later on) plus the first ten years of this 1900s. by RobertoReport definition