What did Marx mean by the alienation of workers under capitalism?

In the context of Marxism, Karl Marx used the concept of alienation to describe how the capitalist system estranges workers from their own humanity and creative potential. Marx argued that under capitalism, work is not a spontaneous or fulfilling expression of human nature, but a compelled activity where the worker becomes a mere commodity in the labor market.1

Specifically, Marx identified four dimensions of this alienation:

• The product: Workers do not own the goods they produce; instead, these products are expropriated by capitalists to be used against the workers.12
• The process: Under factory conditions, the production process is controlled by others, reducing the worker to an "appendage of the machine".2
• Human potential: Workers are denied the satisfaction of using their unique human capacities creatively, as their labor is reduced to a means of survival.23
• Other human beings: Workers are alienated from one another, viewing their peers as rivals competing for jobs and wages.2

Ultimately, Marx viewed this as an objective condition where the worker loses their connection to their own existence, becoming a stranger in the world they help create.3