Anicca
Anicca (Pali; Sanskrit: anitya): All things and experiences are inconstant, unsteady, and impermanent. Everything is made up of parts, and is dependent on the right conditions for its existence. Everything is in flux, and so conditions are constantly changing. Things are constantly coming into being, and ceasing to be. Nothing lasts.

Dukkha
Dukkha (Pali; Sanskrit: duhkha): Because we fail to truly grasp the first two conditions, we suffer. We desire a lasting satisfaction, but look for it amongst constantly changing phenomena. We perceive a self, and act to enhance that self by pursuing pleasure, and seek to prolong pleasure when it too is fleeting.

It is by realizing (not merely understanding intellectually, but making real in one's experience) the three marks of conditioned existence that one develops Praj?a, which is the antidote to the ignorance that lies at the root of all suffering.