退换的英文：
exchange a purchase

参考例句：

Sale goods in this shop are not exchangeable.
本店货物售出概不退换。

I would like to refund this mobile phone.
我想退换这个手机。

You're buying a used car? Caveat Emptor .
你买了一辆二手车吗？货物出门，概不退换。

exchange是什么意思：
n. 交换，互换，交流；兑换，汇率；交易所
v. 交换，互换；交流；兑换

regional exchange
美国在纽约以外地区的证券交易所

This exchange takes place in the foreign exchange market.
汇兑是在外汇交易市场上进行的。

He gambles on the stock exchange.
他从事股票投机。

Sometimes we exchange with words.
有时我们相互交谈几句。

I'll exchange it for a token.
我给你换个专用辅币。

purchase是什么意思：
v. 购买；赢得
n. 购买；紧握

purchase freedom with Blood
以血的代价赢得自由

This orchard became ours by purchase.
这个果树园被我们买下了。

such as stores requisition, purchase requisition,
像库存调拨单，购物申请单，

He purchased this stamp at an auction.
他在拍卖会中购得这枚邮票。

Their purchase is purely a paper transaction.
他们的购买完全是纸上交易。