The used thing you hand over to a seller as part of the payment for the new thing you are buying from them. You buy a new car for 800,000, you give them your old car, they say the old car is worth 200,000, and you pay 600,000 — the old car is the trade-in, and the 200,000 is the trade-in value or trade-in price. It is most often about cars, but the same arrangement runs on phones, computers, cameras, and farm machinery.

for the new thing you are buying from them為了你正向對方買的新東西， to a seller交給賣家、 as part of the payment當作一部分付款、 you hand over你交出去的 The used thing那件用過的舊東西。 You buy a new car你買一輛新車 for 800,000花八十萬， you give them你把 your old car舊車給他們， they say他們說 the old car is worth舊車值 200,000二十萬， and you pay於是你付 600,000六十萬—— the old car舊車 is就是 the trade-in， and而 the 200,000那二十萬 is就是 the trade-in value or trade-in price折抵價值或折抵價。 It它 is most often about最常見於 cars汽車， but但 the same arrangement同樣的做法 on phones在手機、 computers電腦、 cameras相機 and farm machinery和農業機具上 runs也都在運作。

Note the difference the hyphen makes: 'trade-in' with a hyphen is the noun (the object, or the deal), while 'trade in' as two words is the verb — 'I traded in my old phone'. It is used as an adjective too, in front of another noun: trade-in value, trade-in offer, trade-in allowance.

the hyphen makes連字號造成的 the difference差別 Note要注意： with a hyphen帶連字號的 'trade-in' is the noun是名詞 (the object那件東西 or the deal或那筆交易)， while而 as two words分成兩個字的 'trade in' is the verb是動詞—— 'I traded in my old phone'「我把舊手機拿去折抵了」。 It它 too也 as an adjective會當形容詞 used用， in front of another noun放在另一個名詞前面： trade-in value折抵價值、 trade-in offer折抵方案、 trade-in allowance折抵金額。

The tone is ordinary commercial English, neither formal nor slang, and it is the standard word in a showroom.

The tone語氣 is是 ordinary commercial English平常的商業英文， neither formal nor slang不正式也不是俚語， and it而它 in a showroom在展示中心裡 is the standard word就是那個標準用字。