part exchange
noun [ S or U ] UK uk/ˌpɑːt ɪksˈtʃeɪndʒ/ us/ˌpɑːrt ɪksˈtʃeɪndʒ/
部分抵价交易，以旧换新交易
a way of paying for a new object that involves giving your old one as part of the payment
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。