die Achterbahn
roller coaster
An amusement park ride with a rail-based track that has steep drops and fast curves.
Die Kinder schrien vor Freude, als sie mit der Achterbahn fuhren.
The children screamed with joy as they rode the roller coaster.

roller coaster
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roller coaster
An amusement park ride with a rail-based track that has steep drops and fast curves.
Die Kinder schrien vor Freude, als sie mit der Achterbahn fuhren.
The children screamed with joy as they rode the roller coaster.

The word is made up of 'Achter' and 'Bahn'. The name comes from the fact that early roller coasters often had a track in the shape of a figure eight (8).
Die alte Holzachterbahn hat eine klassische Acht als Streckenverlauf.
The old wooden roller coaster has a classic figure-eight track layout.
When talking about riding a roller coaster, you use the fixed construction 'mit der Achterbahn fahren' (to ride the roller coaster).
Bist du schon einmal mit dieser neuen Achterbahn gefahren?
Have you ever ridden this new roller coaster?
You can recognize the figurative meaning from words like 'Gefühle' (feelings), 'Leben' (life), or 'Beziehung' (relationship). The literal meaning is found in the context of amusement parks or fairs.
Ihre Beziehung war eine ständige Achterbahn.
Their relationship was a constant roller coaster.
In the figurative meaning, the combination 'Achterbahn der Gefühle' (emotional roller coaster) is a very common fixed expression.
Nach der Trennung erlebte sie eine wahre Achterbahn der Gefühle.
After the breakup, she experienced a real emotional roller coaster.
fluctuation / swaying
'die Schwankung' and 'die Achterbahn' can both describe a strong up and down. 'Schwankung' is more neutral and more precise when talking about values, prices, temperatures, or even moods. It describes the fact that something does not stay the same. 'Achterbahn' is used figuratively in this context, especially for strong emotions or very changeable situations. Learners may confuse the words because, for example, you can talk about 'emotionale Schwankungen' (emotional fluctuations) and about 'eine emotionale Achterbahn' (an emotional roller coaster). 'Schwankung' sounds more factual; 'Achterbahn' sounds more vivid and stronger.

Nach der Prüfung war meine Stimmung eine echte Achterbahn.
After the exam, my mood was a real roller coaster.
Bei den Preisen gibt es diese Woche eine deutliche Schwankung.
There is a noticeable fluctuation in prices this week.