the three most important cities (esp. in ref. to Tokyo, Osaka, Nagoya)
The Three Major Duties (education, work and payment of taxes)
three greatest teas of Japan (Uji-cha, Sayama-cha and Shizuoka-cha)
the three grand national holidays (Prayer to the Four Quarters, Empire Day, the Emperor's Birthday; pre-1927)
three major diseases (cancer, cerebral stroke, acute myocardial infarction)