experience有复数么,experience为什么不可数名词

experience作“(一次)经历；体验”解时,是可数名词；作“经验”解时,是不可数名词.例如：It was her first experience of living alone.那是她第一次单独生活.He has many interesting experiences in his life.他的一生中有很多有趣的经历.She has years of experience in teaching.她有多年的教学经验.