expend较正式用词，通常指为某一专门目的而花费大量金钱、时间或精力；
spend普通用词，与cost基本同义，意思是花费、消耗、度过，但主语必须是人。
相关介绍
例句：
She expended all her efforts on the care of home and children.
她把所有精力都花在料理家务和照顾孩子上。
Children expend a lot of energy and may need more high-energy food than adults.
孩子们消耗很多能量，可能比成年人需要更多高能量的食物。
I think it is safe to say that very few students expend the effort to do quality work in school
我认为可以肯定地说学校里很少有学生肯为学好功课下功夫。
I spent what little time I had with my family.
我仅有的一点儿时间都和家人在一起度过了。
The money could be better spent on more urgent cases.
这笔钱用于较紧迫的事情也许会好些。
I spent most time on the first question.
我在第一个问题上花的时间最多。
