maintain 指保持原样，不增不减
conserve 较正式用词，指小心地使用难以补充的资源或贵重物，免遭浪费或毁坏，以备不时之需。
preserve 侧重将物品完好无损地保存下来。
save 普通用词，指尽量少用，以争取数量上有所增加。
store 普通用词，指将物品存放，以备将来使用。
参考例句
1. I'll come early tomorrow in order to save your waiting. 明天我会早来点儿，省得让你等着。
2. Oh, my god, who can save me ! 哦，我的上帝，谁可以来拯救我？
3. To save time is to lengthen life. 节约时间根本那是延长生命。
英英解释
n.
1. (sports) the act of preventing the opposition from scoring
2. save from ruin, destruction, or harm
3. to keep up and reserve for personal or special use
4. bring into safety
5. spend less; buy at a reduced price
6. feather one's nest; have a nest egg
7. make unnecessary an expenditure or effort
8. save from sins
9. refrain from harming
10. spend sparingly, avoid the waste of
11. retain rights to
