The term Dasein is central to Heidegger’s philosophy, especially as formulated in Sein und Zeit . The word usually translates from German as “existence” and is formed by compounding da (there) and sein (to be) to form a concept “being-there” or “being-here”. As the word has a particularly rich inflection in the work of Heidegger and is not translated into English in his works, so it has come to be used in philosophical and critical discourse in English as signifying the phenomenological understanding of what it means “to be-in-the-world”.
Editors. "Dasein". The Literary Encyclopedia. First published 04 February 2005
[http://www.litencyc.com/php/stopics.php?rec=true&UID=1523, accessed 20 June 2013.]