twenty-one

n.

二十一，二十一个所成之一组；

1. Oh, I wish to goodness I were twenty one.
   嗨，我要是二十一岁就好了。
2. Next monday is my birthday of twenty first.
   下星期一是我二十一岁的生日。

Democracies. Patterns of Majoritarian and Consensus Government in Twenty-one Countries. By Arend Lijphart
Knee osteoarthritis after meniscectomy: Prevalence of radiographic changes after twenty‐one years, compared with matched controls
Epidemiological transition of stroke in China: twenty-one-year observational study from the Sino-MONICA-Beijing Project.
Epidemiological Transition of Stroke in China:Twenty-One–Year Observational Study From the Sino-MONICA-Beijing Project.pdf
Twenty-One at TREC7: Ad-hoc and Cross-Language Track.
Twenty-one-year trends in the use of inferior vena cava filters.
Stress fractures of the tarsal navicular. A retrospective review of twenty-one cases.
Twenty-one-year trend in ESRD due to focal segmental glomerulosclerosis in the United States.
Three hundred and twenty-one periprosthetic femoral fractures.
Twenty one years of P19 cells: what an embryonal carcinoma cell line taught us about cardiomyocyte differentiation.