Dasein is a German noun invented by Martin Heidegger derived from da sein, which literally means being around. Synonymous with existence, as in I am pleased with my existence (ich bin mit meinem Dasein zufrieden).

In the works of Heidegger, a German word for a being that is capable of recursively comprehending the primal (ontological) authentic (ontic ) nature of its own Being. Heidegger defined the term and concept of Dasein in Being and Time because he needed it to uncover the primal nature of "Being" which Aristotle and Kant left unexplored in their earlier ideas of ontology.

Dasein is a special entity in that it is simultaneously ontological (does) and ontic (is) in that its pursuit of itself is in fact the pursuit of the pursuit of itself; the primal nature of Dasein is authentic and recursive. Dasein is just the way we are. Traditions of language, logical system, or belief may obscure Dasein's authentic primal nature from itself. Beings are Dasein even when they are ontologically wrapped up in a tradition which obscures the authentic choice to live within and transmit this tradition. In this case Dasein still authentically chooses the tradition when it is confronted by a paradox within the tradition and must choose to dismiss the tradition or dismiss the experience of being confronted with choice.

Heidegger attempted to maintain the definition of Dasein as we all are, in our average everydayness. Dasein does not spring into existence upon philosophical exploration of itself. Heidegger intended Dasein as a concept, in order to provide a stepping stone in the questioning of what it means to be . When Dasein contemplates this, what seems (absurdly) circular in ontic terms, is recursive in ontological sense, because it brings the necessary appearance of time to the center of attention. Dasein is a way to get at an ontological understanding of time.