nochmal
again
Means 'noch einmal' (once again) or 'wieder' (again). It expresses the repetition of an action or process.
Könntest du das bitte nochmal wiederholen?
Could you please repeat that again?

again
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again
Means 'noch einmal' (once again) or 'wieder' (again). It expresses the repetition of an action or process.
Könntest du das bitte nochmal wiederholen?
Could you please repeat that again?

'Nochmal' is the colloquial and very common shortened form of 'noch einmal' (once again). In everyday speech, 'nochmal' is almost always used. 'Noch einmal' sounds more formal or emphasizes the repetition more strongly.
Entschuldigung, ich habe das nicht verstanden. Können Sie das nochmal sagen?
Excuse me, I didn't understand that. Can you say it again?
As an adverb, 'nochmal' usually stands in the middle field of the sentence, that is, after the conjugated verb and often also after the subject.
Ich muss dich nochmal etwas fragen.
I need to ask you something again.
'Nochmal' is very often used in requests and commands to ask for a repetition. It can also pick up a thought again or summarize and confirm information.
Mach die Übung bitte nochmal, sie war nicht ganz richtig.
Please do the exercise again; it wasn't quite right.
again / back
'wieder' and 'nochmal' can both mean that something happens one more time. 'nochmal' is especially natural in spoken language, for example in requests or when you want to repeat something directly. 'wieder' is more general and also fits when something happens again after a break or returns to an earlier state. Learners may confuse the words because both often mean 'noch einmal' (once again). As a simple guide: for a direct repetition, 'nochmal' often fits; for a renewed situation after some time, 'wieder' often fits.

Kannst du den Satz bitte nochmal sagen?
Can you please say the sentence again?
Der Kunde ruft morgen wieder an.
The customer will call again tomorrow.