unweigerlich
inevitably
In such a way that it cannot be avoided; necessarily or unavoidably.
Wenn man zu viel isst, führt das unweigerlich zu einer Gewichtszunahme.
If you eat too much, it inevitably leads to weight gain.

inevitably
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inevitably
In such a way that it cannot be avoided; necessarily or unavoidably.
Wenn man zu viel isst, führt das unweigerlich zu einer Gewichtszunahme.
If you eat too much, it inevitably leads to weight gain.

The word is made up of 'un-' (un-), the stem of 'weigern' (to refuse; sich weigern, etwas zu tun = to refuse to do something), and the ending '-lich' (-ly/-able). So it describes something that one cannot “refuse away” or avoid.
Die ständige Nutzung des Handys führt unweigerlich zu Nackenschmerzen.
Constant use of a mobile phone inevitably leads to neck pain.
'Unweigerlich' (inevitably) is almost always used as an adverb that modifies a verb or an entire sentence. It often comes directly after the conjugated verb in a main clause.
Ohne Training wird man unweigerlich schlechter.
Without training, you will inevitably get worse.
Common verbs combined with 'unweigerlich' (inevitably) are 'führen zu' (to lead to), 'folgen' (to follow), or 'passieren' (to happen), to express an inevitable consequence.
Eine solche Politik führt unweigerlich zu sozialen Spannungen.
Such a policy inevitably leads to social tensions.
This word belongs more to written language or an elevated style. It is used less often in everyday colloquial speech.
Der technologische Fortschritt bringt unweigerlich Veränderungen mit sich.
Technological progress inevitably brings changes with it.
inevitable
'zwangsläufig' and 'unweigerlich' have very similar meanings: something cannot be avoided. Both fit when a consequence is certain to happen. 'zwangsläufig' often emphasizes the logical consequence of a situation. 'unweigerlich' emphasizes more strongly that something is certain to come and cannot be stopped. In many sentences, you can use both words. 'zwangsläufig' sounds especially appropriate in explanations and causes, while 'unweigerlich' is often used for consequences that are certain to happen.

Ohne klare Absprachen kommt es im Team unweigerlich zu Missverständnissen.
Without clear agreements, misunderstandings will inevitably arise within the team.
Wer zu wenig schläft, ist am nächsten Tag nicht zwangsläufig krank, aber oft müde.
Someone who sleeps too little is not necessarily sick the next day, but is often tired.