此在（德語： ）呢個詞係海德格爾喺佢嘅鉅著《存在與時間》入面提出嘅哲學概念。Dasein呢個術語無辦法翻譯成中文，但可以知道佢係由兩個詞組成：da（此時此地）同埋sein（存有、是）。為咗方面表達da同埋sein嘅關係，有時都會譯成“親在”同埋“緣在”，而“此在”呢個譯法係依家比較普遍嘅譯名。但如果要理解「此在」呢個術語時，唔可以單純將da理解做此時此地，而係要先領會“存在”呢個詞語然後再對存在方式作一個延伸而得出。
The word "in" is a philosophical concept proposed by Heidegger in his magnum opus, Being and Time. The term Dasein cannot be translated into Chinese, but it is known that it is composed of two words: da (here and now) and sein (existence, is). In order to express the relationship between da and sein in this regard, it is sometimes translated as "kin-in" and "yuan-in", and the translation of "this-in" is now a more common translation. However, if we want to understand the term "here and now", we should not simply understand da as here and now, but first grasp the word "being" and then extend the mode of existence.