zurückzahlen
to pay back
To return borrowed money to the creditor.
Ich muss meinen Studienkredit in den nächsten zehn Jahren zurückzahlen.
I have to pay back my student loan over the next ten years.

to pay back
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to pay back
To return borrowed money to the creditor.
Ich muss meinen Studienkredit in den nächsten zehn Jahren zurückzahlen.
I have to pay back my student loan over the next ten years.

'Zurückzahlen' (to pay back) is a separable verb. The prefix 'zurück' comes at the end in main clauses. In subordinate clauses or in the infinitive with 'zu', the verb stays together.
Sie zahlt ihm das geliehene Geld nächste Woche zurück.
She is paying him back the borrowed money next week.
The verb is made up of the adverb 'zurück' (back) and the verb 'zahlen' (to pay). The meaning is literal: you return a payment to its origin.
Wann kannst du mir die 50 Euro zurückzahlen?
When can you pay me back the 50 euros?
The person who receives the money or deed back is always in the dative. What is paid back is in the accusative. The structure is: jemandem (dative) etwas (accusative) zurückzahlen.
Ich muss der Bank (Dativ) den Kredit (Akkusativ) zurückzahlen.
I have to pay back the loan (accusative) to the bank (dative).
In the financial meaning, the verb is typically combined with nouns such as 'Schulden' (debts), 'einen Kredit' (a loan), 'ein Darlehen' (a loan), or simply 'Geld' (money).
Er hat all seine Schulden vollständig zurückgezahlt.
He has paid back all his debts in full.
In the figurative meaning, 'zurückzahlen' (to pay back) can express both revenge and gratitude. The phrase 'Das zahle ich dir zurück!' (I'll pay you back for that!) is often a threat.
Für deine Hilfe werde ich es dir eines Tages zurückzahlen.
I will pay you back for your help one day.
to pay
'bezahlen' and 'zurückzahlen' both have to do with money. You use 'bezahlen' when you give money for something, for example for a meal, a bill, or a service. You use 'zurückzahlen' only when you previously borrowed money and later give it back to the person or bank. Learners may confuse the words because in both cases money changes hands. The important difference is: 'bezahlen' is about a price or a debt, while 'zurückzahlen' is about borrowed money.

Nach dem Unterricht zahlt sie ihrer Freundin das geliehene Geld zurück.
After class, she pays her friend back the money she borrowed.
Der Gast bezahlt die Rechnung direkt mit Karte.
The guest pays the bill directly by card.