A trade-in; exchanging an old item (car, furniture, etc.) with a seller who deducts its value from the price of a new purchase.
古い車を下取りに出して新車を買った。
I traded in my old car and bought a new one.
家具店でソファを下取りしてもらい、差額だけ支払った。
The furniture store took my sofa as a trade-in and I paid only the difference.
店は下取り額を査定して見積もりを出してくれた。
The shop appraised the trade-in value and gave me an estimate.