Finally the remaining characteristic, which is common to all phenomena, is that of Dukkha. Dukkha, as used within a Buddhist context, does not have a direct English equivalent. The usual rendering is 'unsatisfactoryness'. This may well be technically correct, but it does nothing for the practical meditator or aspiring contemplative, that I assume to be the typical reader of this Web page. For myself, the most widely applicable equivalents are 'anguish', 'despair' or even 'frustration'.
Feeling can be pleasant or unpleasant, and thus categorize our entire field of experience.
Pleasant experiences can be seen as anguish because they do not last in time. Thus, all things can appear to be anguish, despairing or frustrating, hence, dukkha. When any of these three characteristics are seen with sufficient detachment and clarity there is a resulting sense of insight, which leads to dispassion and Nibbana, which unsurprisingly enough exhibits the characteristic spaciousness of No-Self. For the new practitioner, with a lot of pent up, inefficient and dissipated energy, just waiting for the flood gates to burst open, this can happen quite suddenly. Any progressive, or intermediate, stages become telescoped and indistinguishable.