[] () the theory that sales of a product pass through four stages: introduction, when there is a gradual increase in sales; growth, when sales increase rapidly; maturity , when sales increase slowly; decline, when sales fall产品生命周期（产品销售要经历四个阶段：销量逐步增长的导入期；销量迅速增长的成长期；销量缓慢增长的成熟期；销量下降的衰退期）◆With personal computers and software, the trend is toward shorter and shorter product life cycles.个人计算机和软件的产品生命周期趋于越来越短。