time 与 period的区别

period与time的区别? time 与 period的区别 it's + a period of time + before/since 的区别? 与between the time period of相似的短语 transition period和transitional period的区别? time period 的意思是什么? epoch age period time era 区别 overhead和period cost的区别概念 "product cost"和 "period cost"的区别 no time与any time的区别 time over与time out 的区别 on time与in time的区别