إِنَّ الْإِنْسَانَ لَفِي خُسْرٍ
Surely humankind is in loss.
The definite article al- can mark an already identifiable individual (‘ahd) or the relevant kind or class (jins). These uses yield different readings even though the visible article is the same.
In «الإنسان», the discussion concerns humankind rather than one named person. In another setting «الرجل» might denote a particular man already identifiable. The surrounding statement determines which reading fits.