unverzichtbar
indispensable
Absolutely necessary or essential; so important that one cannot do without it.
Für diese Position sind gute Englischkenntnisse unverzichtbar.
Good English skills are indispensable for this position.

indispensable
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indispensable
Absolutely necessary or essential; so important that one cannot do without it.
Für diese Position sind gute Englischkenntnisse unverzichtbar.
Good English skills are indispensable for this position.

The word is built logically: the prefix 'un-' negates, 'verzicht-' comes from 'verzichten' (to do without), and the ending '-bar' means 'possible'. So 'unverzichtbar' (indispensable) literally means 'not possible to do without'.
Ein gutes Wörterbuch ist für Sprachlerner unverzichtbar.
A good dictionary is indispensable for language learners.
'Unverzichtbar' (indispensable) is very often used with the preposition 'für' (for) and the accusative. This construction expresses for whom or for what something is necessary.
Regelmäßige Pausen sind für die Konzentration unverzichtbar.
Regular breaks are indispensable for concentration.
'Unverzichtbar' (indispensable) is often combined with abstract nouns to emphasize their importance. Typical examples are: 'ein unverzichtbarer Teil' (an indispensable part), 'ein unverzichtbares Werkzeug' (an indispensable tool), or 'eine unverzichtbare Voraussetzung' (an indispensable prerequisite).
Teamfähigkeit ist eine unverzichtbare Eigenschaft für diesen Job.
Teamwork skills are an indispensable quality for this job.
necessary
'nötig' and 'unverzichtbar' are close in meaning because both say that something is needed. 'nötig' is more general and neutral: something is 'nötig' if it is needed for a purpose. 'unverzichtbar' is stronger and means that you can hardly manage without that thing. It emphasizes that something is very important. For normal conditions, 'nötig' is often enough. For something especially important or essential, 'unverzichtbar' is more precise.

Im Winter ist eine warme Jacke für lange Spaziergänge unverzichtbar.
In winter, a warm jacket is indispensable for long walks.
Für mehr Sicherheit zu Hause ist ein gutes Schloss nötig.
For greater safety at home, a good lock is necessary.