'Foreigner' siempre se refiere a una persona [del extranjero] mientras 'foreign' se usa cuando uno esta hablando sobre un objeto.
e.g., The French Minister of Trade hopes the bill banning foreign wine will soon be passed.
Foreigners in Canada are free to stay in the country for three months, but are not permitted to work without a permit.
Nota: Tambien se puede usar "foreign" para referirse a personas. Ejemplo: "There are many foreign people in Toronto." (foreign people = foreigners).
P.S. "Acabo de lleguar del extranjero" = "I just came back from abroad"
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