part exchange

/ˌpɑːt ɪksˈtʃeɪndʒ/

a way of paying for a new object that involves giving your old one as part of the payment

部分抵价交易，以旧换新交易

If you give an old item in part exchange for something you are buying, the seller accepts the old item as part of the payment, so you do not have to give them as much money.

如果你用旧物品做了part exchange来去买你要的东西，那么就是说卖家会接受旧物品作为付款的一部分，所以你不需要用正价来买。

I might offer them my old camera in/as part exchange for a new one.

我可以用我的旧相机部分抵价来买一台新相机。