The word "alienated" is, of course, the past tense of the verb: to alienate.
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Karl Marx used the term alienation (or, in his German writing Entfremdung or Entäusserung) to refer to the separation of things that naturally belong together, or antagonism between things that are properly in harmony.
When people's ‘being does not correspond to their essence’ they are alienated, while actualisation (its opposite) is ‘the extent to which the human being as species being, as a human being, has become himself and grasped himself’.
Alienation is also caught up with the perceived monotony of the work of the proletarian under the capitalist division of labour.