der Fünfer
fiver
A coin or banknote worth five currency units, especially five euros.
Hast du einen Fünfer für den Parkautomaten?
Do you have a fiver for the parking meter?

fiver
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fiver
A coin or banknote worth five currency units, especially five euros.
Hast du einen Fünfer für den Parkautomaten?
Do you have a fiver for the parking meter?

'Fünfer' (fiver/five) is derived from the number 'fünf' (five). The ending '-er' turns the number into a noun that refers to something connected with that number.
Gib mir bitte einen Zehner, dann bekommst du zwei Fünfer zurück.
Give me a tenner, please, and you'll get two fivers back.
The word 'Fünfer' (fiver/five) is used mainly in colloquial language in all its meanings. It is a short, everyday form for 'Fünf-Euro-Schein' (five-euro note), 'Note 5' (grade 5), or 'Linie 5' (line 5).
Ich nehme immer den Fünfer zur Arbeit.
I always take the five to work.
The context makes it clear which meaning is intended. If it is about money and paying, it means a coin or banknote. In connection with school and grades, it is a school grade. With means of transport, it refers to a bus or train/tram line.
Ich habe nur noch einen Fünfer im Portemonnaie.
I only have a fiver left in my wallet.
In the context of school grades, 'Fünfer' (grade five) is often used with verbs like 'bekommen' (to get), 'kriegen' (to get), or 'schreiben' (to get/write on a test).
Ich habe hart gelernt, um keinen Fünfer zu bekommen.
I studied hard so I wouldn't get a grade five.
five
'fünf' and 'der Fünfer' are both connected to the number 5. 'fünf' is the normal number word: you say 'fünf Minuten' (five minutes), 'fünf Euro' (five euros), or 'Note fünf' (grade five). 'der Fünfer' is a noun and needs an article. It can refer to a five-euro note, the grade 5, or also a number such as a bus line. The words can be confused because both point to the same number. In practice: if you are simply naming a quantity, use 'fünf'. If you mean a specific thing with the number 5, 'der Fünfer' often fits.

Kannst du mir einen Fünfer wechseln?
Can you change a fiver for me?
Für den Kuchen brauchen wir fünf Eier.
We need five eggs for the cake.