der Käufer
buyer
A person or organization that acquires goods or a service in exchange for payment.
Der Käufer des Hauses hat den Vertrag gestern unterschrieben.
The buyer of the house signed the contract yesterday.

buyer
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buyer
A person or organization that acquires goods or a service in exchange for payment.
Der Käufer des Hauses hat den Vertrag gestern unterschrieben.
The buyer of the house signed the contract yesterday.

The word 'Käufer' is derived directly from the verb 'kaufen' (to buy). The ending '-er' is often added to verbs in German to indicate the person who performs that action.
Wer ist der Käufer dieses alten Schranks?
Who is the buyer of this old cabinet?
If you want to express what a buyer is being sought for or what was bought, use the preposition 'für' followed by the accusative.
Es ist nicht leicht, einen Käufer für ein so teures Auto zu finden.
It is not easy to find a buyer for such an expensive car.
Common combinations are 'einen Käufer finden' (to find a buyer), 'ein potenzieller Käufer sein' (to be a potential buyer), or contrasting 'Käufer und Verkäufer' (buyer and seller).
Für das renovierte Bauernhaus gibt es bereits mehrere potenzielle Käufer.
There are already several potential buyers for the renovated farmhouse.
The economic meaning can often be recognized by signal words such as 'Börse' (stock exchange), 'Aktien' (stocks), 'Markt' (market), or 'Angebot und Nachfrage' (supply and demand). In this context, the word pair 'Käufer und Verkäufer' (buyers and sellers) occurs especially often.
Wenn es mehr Käufer als Verkäufer gibt, steigt der Preis der Aktie.
If there are more buyers than sellers, the price of the stock rises.
customer
'der Kunde' and 'der Käufer' can both refer to a person who pays for something and receives it. 'Kunde' fits especially when the relationship with a shop, company, or service provider is involved. A customer may come regularly or receive advice. 'Käufer' puts more emphasis on the individual purchase. The word is more precise when someone has really bought something or wants to buy something. They can be confused because a customer is often also a buyer. But not every customer is a buyer at that moment, for example if they are only asking a question.

Der Käufer bezahlt das Fahrrad und nimmt es sofort mit.
The buyer pays for the bicycle and takes it with him right away.
Der Kunde wartet an der Kasse, weil er eine Frage zur Rechnung hat.
The customer waits at the checkout because he has a question about the bill.