viermal
four times
Indicates the number four; four times.
Ich habe viermal geklingelt, aber niemand hat die Tür geöffnet.
I rang the bell four times, but no one opened the door.

four times
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four times
Indicates the number four; four times.
Ich habe viermal geklingelt, aber niemand hat die Tür geöffnet.
I rang the bell four times, but no one opened the door.

The word is made up of the number 'vier' (four) and the ending '-mal' (times). This structure is used for all counting adverbs to indicate repetition, e.g. 'einmal' (once), 'zweimal' (twice), 'dreimal' (three times).
Ich habe dir das jetzt schon zehnmal erklärt.
I've already explained that to you ten times now.
As an adverb, 'viermal' (four times) can stand in different places in the sentence. If it is in position 1, the verb follows directly after it. But it can also stand in the middle of the sentence.
Viermal habe ich versucht, dich anzurufen.
Four times I tried to call you.
'Viermal' (four times) is often used to indicate the frequency of an action within a period of time. Typical combinations are 'viermal pro Woche' (four times per week), 'viermal im Jahr' (four times a year), or 'viermal hintereinander' (four times in a row).
Der Kurs findet viermal pro Woche statt.
The course takes place four times per week.
four
'vier' and 'viermal' both relate to the number 4. The difference is in how they are used: 'vier' counts people, things, or amounts. 'viermal' says how often something happens. Learners may confuse the words because both contain the same number. If you are asking 'How many?', 'vier' usually fits. If you are asking 'How often?', 'viermal' fits.

Vor dem Wettkampf trainiert er viermal pro Woche.
Before the competition, he trains four times a week.
In unserer Gruppe sind heute nur vier Teilnehmer.
There are only four participants in our group today.