unvermeidbar
unavoidable
Something that cannot be prevented or avoided and will certainly happen.
Aufgrund des Streiks waren Verspätungen im Zugverkehr unvermeidbar.
Because of the strike, delays in train service were unavoidable.

unavoidable
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unavoidable
Something that cannot be prevented or avoided and will certainly happen.
Aufgrund des Streiks waren Verspätungen im Zugverkehr unvermeidbar.
Because of the strike, delays in train service were unavoidable.

The word is logically structured: the prefix 'un-' means 'not', the stem comes from the verb 'vermeiden' (to avoid), and the ending '-bar' means 'possible'. So 'unvermeidbar' (unavoidable) is something that one cannot avoid.
Einige Fehler sind am Anfang unvermeidbar.
Some mistakes are unavoidable at the beginning.
'Unvermeidbar' (unavoidable) is very often used predicatively with the verb 'sein' (to be). The structure is then: 'Etwas ist unvermeidbar' (Something is unavoidable).
Eine Preiserhöhung war leider unvermeidbar.
A price increase was unfortunately unavoidable.
This adjective often describes negative or neutral events and their results. Typical nouns are 'Folgen' (consequences), 'Konsequenzen' (consequences), 'Verluste' (losses), or 'Konflikte' (conflicts).
Der Klimawandel hat unvermeidbare Folgen für die Umwelt.
Climate change has unavoidable consequences for the environment.
inevitable
'zwangsläufig' and 'unvermeidbar' are very close in meaning because both say that something cannot happen any other way. 'unvermeidbar' directly says that something cannot be prevented or avoided. 'zwangsläufig' often additionally emphasizes that something arises as a logical consequence of a particular situation. If you only want to say that something cannot be avoided, 'unvermeidbar' works very well. If you want to show the connection between cause and effect, 'zwangsläufig' often sounds more precise.

Im Krankenhaus ist eine kurze Wartezeit heute unvermeidbar.
At the hospital, a short wait is unavoidable today.
Mehr Verkehr führt in der Innenstadt zwangsläufig zu längeren Wartezeiten.
More traffic inevitably leads to longer waiting times in the city center.