〖英文學習〗時距（Intervals of time ）
Semidiurnal: twice a day
Diurnal: daily
Biweekly: twice a week or every two weeks
Semiweekly: twice a week
Weekly: once a week
Bimonthly: twice a month or every two months
Triweekly: three times a week or every 3 weeks
Semimonthly: twice a month
Monthly: once a month
Trimonthly: every three months
Quarterly: four times a year
Biannual: twice a year
Semiannual: every six months
Annual: yearly
Perennial: occurring year after year
Biennial: 2 years
Triennial: 3 years
Quadrennial: 4 years
Quinquennial: 5 years
Sexennial: 6 years
Septennial: 7 years
Octennial: 8 years
Novennial: 9 years
Decennial: 10 years
Undecennial: 11 years
Duodecennial: 12 years
Quindecennial: 15 years
Vicennial: 20 years
Tricennial: 30 years
Quadricennial: 40 years
Semicentennial: 50 years
Centennial: 100 years
Sesquicentennial: 150 years
Bicentennial: 200 years
Quadricentennial: 400 years
Quincentennial: 500 years
Millennial: 1000 years
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