These German adverbs answer the question of how often something happens or is the case — Wie oft? Let's take a look at how to describe the most frequent to least frequent occurrences. 

First of all, we have immer, or "always." Like in English, there are different options for the placement of adverbs in German sentences. In this first sentence, the word einfach is also serving as an adverb, and both adverbs are placed after the verb. 

BANNER PLACEHOLDER

Es ist einfach immer was los und man ist in einer halben Stunde hier oben.

There is simply always something going on and you are up here in half an hour.

Caption 20, 48 h in Innsbruck - Sehenswürdigkeiten & Tipps

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Meistens, häufig and oft describe a relatively common or frequent occurrence. Note that, in this particular example, meistens is in the first position with the verb immediately following, which gives it extra emphasis. In the other two examples, the adverb comes after the verb (although not the participle!). 

Meistens sind ja die Fenster dann auch noch recht schmal.

Most of the time, the windows are also really narrow.

Caption 57, Feuerwehr Heidelberg - Löschfahrzeug

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In Deutschland ist das Wetter im Herbst häufig kühl und feucht.

In Germany, the weather in autumn is frequently cool and damp.

Caption 6, Herbst - mit Eva

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Große Erfindungen werden oft von ungewöhnlichen Ereignissen inspiriert.

Great inventions are often inspired by unusual events.

Caption 3, 200. Geburtstag - Die Geschichte des Fahrrads in 2 Minuten

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From manchmal to selten, the frequency of something happening or being the case decreases rapidly.

Es ist nur manchmal einfach etwas schwierig, wenn man zusammenlebt und so gut befreundet ist.

It is just sometimes a bit difficult when you live together and are such good friends.

Caption 34, Die Wohngemeinschaft - Probleme

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Ab und zu kann es aber auch mal ganz schön laut werden.

Once in a while it can, however, get pretty loud too.

Caption 62, Rhein-Main-TV - Badesee Rodgau

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Seinen schicken Umhang trug er gar nicht mehr,

He no longer wore his chic cloak

und mit seinem Pferd ritt er nur noch selten.

and he rode his horse only rarely.

Captions 38-39, Märchen - Sagenhaft - Die Prinzessin auf der Erbse

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Finally, we come to "never." It is also possible to say fast nie or "almost never."

Also, früher wollt ich nie zum Klavierunterricht gehen.

Well, at the time I never wanted to go piano lessons.

Caption 35, Deutsche Bands - Glashaus

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Further Learning
Many examples of these words can be found on Yabla German, and you can also look up the following German adverbs of definite frequency: täglich, wöchentlich, monatlich, jährlich, morgens, nachmittags, and abends. For more information on adverb placement, take a look at this helpful page.