Glossery from SuanMokkh.org

ANATTA, not-self, the fact that all things, without exception and including nibbana, are not-self and lack any essence or substance that could properly be regarded as a "self." This fact does not deny the existence of things, but denies that they can be owned or controlled, that they can be the owner or controller, in any but a relative, conventional sense.

ANICCA, impermanent (or aniccata, impermanence), flux, instability. Conditioned things are ever-changing, constantly arising, manifesting, and ceasing. This is the first fundamental characteristic of conditioned things.

ATTA, self, ego, soul, (Sanskrit, atman): the instinctual feeling (and illusion) that there is some "I" who does all the things to be done in life. Through ignorance and wrong understanding this instinctual sensibility is attached to and becomes "ego." No personal, independent, self-existing, free-willing, lasting substance or essence can be found anywhere, whether within or without human life and experience, not even in "God." (Cf. anatta, idappaccayata, and suññata.)

AVIJJA, ignorance, not-knowing, wrong knowledge: the lack, partial or total, of vijja (correct knowledge) regarding the things that need to be known (e.g., the four noble truths, suññata, tathata), as well as knowing things in the wrong way, i.e., as permanent, satisfying, and self. The most original cause of all dukkha. Without Dhamma practice, ignorance grows into increasingly wrong knowledge.

ANAPANASATI, mindfulness with breathing in and out: the only meditation or vipassana system practiced and taught by the Buddha, it covers all four foundations of mindfulness and perfects the seven factors of awakening, leading to liberation. Ajarn Buddhadasa considers it the best way to realize suññata.

DHAMMA, Truth, Nature, Law, Natural Truth, Duty, Order, "the way things are": this impossible to translate word has many meanings, the most important of which are Nature, the Law of Nature, our Duty according to Natural Law, and the Fruits of doing that Duty correctly according to Natural Law. (See paticca-samuppada.)

NIBBANA, coolness, quenching: the Absolute, the Supreme, the Ultimate Reality in Buddhism; the "goal" of Buddhist practice and highest potential of humanity. Nibbana manifests when the fires of defilement, attachment, selfishness, and dukkha are cooled. When they are permanently cooled, nibbana manifests perfectly, totally, timelessly. Not a place, for nibbana is beyond existence and non-existence, not even a state of mind, for nibbana is neither mental nor physical, but a dhamma the mind can realize and experience. To be realized in this life.

NIVARANA, hindrances, obstacles: disturbing moods and mental qualities which interfere with the mind's task, whether worldly or spiritual. Half-strength defilements, they arise from the tendencies toward defilement built up through carelessness and need not be triggered by outside objects. To overcome them, correct samadhi is needed. The traditional list of five are sensual desire, aversion, sloth and torpor, restlessness and distraction, and doubt.