that which threatens has the character of something altogether unfamiliar, then fear becomes dread [Grauen]. And where that which threatens is laden with dread, and is at the same time encountered with the suddenness of the alarming, then fear becomes terror [Entsetzen]. There are further variations of fear, which we know as timidity, shyness, misgiving, becoming startled. All modifications of fear, as possibilities of having a state-of-mind, point to the fact that Dasein as Being-in-the-world is 'fearful' ["furchtsam"]. This 'fearfulness' is not to be understood in an ontical sense as some factical 'individualized' disposition, 1 but as an existential possibility of the essential state-of-mind of Dasein in general, though of course it is not the only one.
¶ 31. Being-there as Understanding
State-of-mind is one of the existential structures in which the Being of the 'there' maintains itself. Equiprimordial with it in constituting this Being is understanding. A state-of-mind always has its understanding, even  if it merely keeps it suppressed. Understanding always has its mood. If we Interpret understanding as a fundamental existentiale, this indicates that this phenomenon is conceived as a basic mode of Dasein's Being. On the other hand, 'understanding' in the sense of one possible kind of cognizing among others (as distinguished, for instance, from 'explaining'), must, like explaining, b e Interpreted as a n existential derivative of that primary understanding which is one of the constituents of the Being of the "there" in general.
We have, after all, already come up against this primordial understanding in our previous investigations, though we did not allow it to be included explicitly in the theme under discussion. To say that in existing, Dasein is its "there", is equivalent to saying that the world is 'there'; its Being-there is Being-in. And the latter is likewise 'there', as that for the sake of which Dasein is. In the "for-the-sake-of-which", existing Being-in-the-world is disclosed as such, and this disclosedness we have called "understanding". vii In the understanding of the "for-the-sake-of-which", the significance which is grounded therein, is disclosed along with it. The disclosedness of understanding, as the disclosedness of the "for-the-sake-of-which" and of significance equiprimordially, pertains to the entirety of Being-in-the-world. Significance is that on the basis of which the world is disclosed as such. To say that the "for-the-sake-of-which" and significance are both disclosed in Dasein, means that Dasein is that entity which, as Being-in-the-world, is an issue for itself.
1 '... im ontischen Sinne einer faktischen, "vereinzelten" Veranlagung ...' While the verb 'vereinzeln' often means 'to isolate', Heidegger does not ordinarily use it in this sense. Indeed he contrasts it with the verb 'isolieren'. Cf. H. 188 below.