noun
plural -penses
[noncount] :the amount of money that is needed to pay for or buy something
If you spare no expense, you spend as much money as you need to in order to make something as good as possible.
[count] :an amount of money that must be spent especially regularly to pay for something
usually plural
[count] :something on which money is spent
at someone's expense
paid for by someone
If someone makes a joke about you or laughs at you, the joke or laughter is said to be at your expense.
at the expense of
in a way that harms (something or someone)
go to (the) expense
to spend money on something