Sentence:  Officials in China are divided into three <WSD>echelons</WSD>, or generations. The first <WSD>echelon</WSD> joined the Communist Party in the 1920s, soon after the party was founded. ... The second <WSD>echelon</WSD> joined the Communist Party before the founding of the People's Republic of China in 1949. The party was then still struggling, and many of the second <WSD>echelon</WSD> died during the wars. They were again true patriots. The third <WSD>echelon</WSD> joined the Communist Party after the founding of the People's Republic. 
Meaning of the word marked with <WSD> tags:  A level or rank in an organization, profession, or society.