1.a period marked by distinctive character or reckoned from a fixed point or event
2.a major division of geological time; an era is usually divided into two or more periods
自责分(Earned Run,通常记为ER),在棒球比赛里指的是对方的得分当中,因为投手的投球所造成的部份(也就是扣除因为失误或是捕逸所造成的失分) 投手自责分率(earned run average,通常记为ERA)又称之为『防御率』(语源为日本汉字「防御率」),其计算门槛是投球局数必须达到所属球队之出赛数的总和(但各联盟可自行规定投球局数,如日本二军以0.8局/场来计算规定局数)。从防御率可得知一个投手每九局大概会失几分,其数值越