Heidegger's term <i>Eigentlichkeit</i> is generally translated into <i>authenticity</i>. This translation often leads us to the assumption that there is something authentic. But Heidegger uses this term to express human <i>Dasein</i>'s modus. He says <i>Dasein</i> is to be grasped through <i>how Dasein</i> is, contrasted with other entities which are grasped through <i>what</i> they are. This means that <i>Dasein</i> is always variable and has no regular modus, including an authentic one. This being taken into consideration, the conclusion is drawn that <i>authenticity</i> is inappropriate to express <i>Eigentlichkeit</i>.<br> The term <i>Eigentlichkeit</i> in the thought of Heidegger is chosen "in a strict sense". The sense of this term lies in <i>eigen</i>, which is <i>own</i> in the primary meaning. Following this, we should translate <i>Eigentlichkeit</i> into <i>own-ness</i> or <i>ownedness</i>(<i>eigen</i>, i. e. <i>own</i> is the past participle in its origin). This translation matches with the way <i>Dasein</i> exists; <i>Dasein</i> exists in a modus in each case, which means that <i>Dasein owns</I> his or her temporary modus in each case. <i>Eigentlichkeit</i> is <i>owned</i> by <i>Dasein</i> in each case. Therefore, Dasein can lose <i>Eigentlichkeit</i> in each case, <i>Dasein</i> can be in its negation(<i>Uneigentlichkeit</i>) in each case.<br> The above matches also with the definition of <i>Eigentlichkeit</i> and <i>Uneigentlichkeit</i>. They are both based on the fact that <i>Dasein</i> is in general determined by <i>mineness-in-each-case</i>(<i>Jemeinigkeit</i>). <i>Dasein</i> is always concerned about whether <i>Eigentlichkeit</i> is <i>owned</i> or not.<br> Heidegger regards the business of philosophy as the preservation of the power of the most elemental words. Otherwise, the words would be flattened by the common understanding and levelled off to that unintelligibility which functions in turn as a source of illusory problems. This is true specifically of the term <i>Eigentlichkeit</i>.