当“费用，成本”讲的时候，是可数名词，加s，作“代价，损失”讲，是不可数名词，不加s。expense可数不可数皆可,做“开支,经费”解释时常用复数形式。不可名词 spending of money etc;可数名词cause of spending。
expense
读音：英 [ɪkˈspens] 美 [ɪkˈspɛns]
释义：n.费用;花费的钱;消耗;花钱的东西
vt.向…收取费用;把…作为开支勾销
第三人称单数： expenses
复数： expenses
现在分词： expensing
过去式： expensed
过去分词： expensed
例句：
1、It was said that he went to great expense to install a lift in the building.
据说他花费巨资在大楼里安装了一台电梯。
2、It was not a fortune but would help to cover household expenses.
这笔钱不算多，但是能帮助支付家庭开支。