Dukkha is one of the most misunderstood Pali words in Buddhism. It is found in the first sermon and in many other discourses dealing with the nature of life or existence. The term embraces many meanings and refers to different things in different contexts.

Buddhism has often been criticized for its alleged pessimistic slant in its world outlook: it has been accused of giving undue emphasis on the many unsatisfactory conditions of existence such as physical sufferings, frustration, disappointment, poverty, and diseases, and overlooking at the same time the pleasurable conditions that are equally available to the world.

Such a criticism is primarily based on the wrong interpretation of the first Noble Truth proclaimed by the Buddha, which attempts to define the nature of the world in realistic perspectives. It is the Noble Truth of Dukkha, popularly, but erroneously, translated as "suffering", "unsatisfactoriness", "pain" and similar terms or phrases, each of which carries but a partial implication of the original Pali expression specifically intended by the Buddha.

It is true that in ordinary usage the word dukkha means suffering, sorrow, etc., as opposed to the word sukha, which implies comfort or happiness. But when it is used in the first Noble Truth to represent the view of life and the world, the term acquires a much profounder philosophical implication. In signifies, beside the ordinary meanings, deeper ideas such as imperfection, impermanence, emptiness, insubstantiality, which are not altogether in the scope of the popular usage.

Buddhism distinguishes three kinds of dukka. To the first category, dukkha-dukkhata, belong all mental and physical experiences that are generally considered as unpleasant, undesirable, and painful, such as, sickness, death, miseries, poverty, agony, distress, discomfort, etc. In other words, dukkah-dukkhata means all kinds of sufferings in the ordinary empirical sense, to which all living beings must be subject albeit in varying degrees as per individual circumstances. It is the most apparent form of dukkha because it can be directly experienced by the senses.

Oftentimes, it is only this category of dukkha-dukkhata that the first Noble Truth is taken to represent, which gives rise to the misconception the Buddhism is pessimistic in its outlook of the world.

The second category of dukkah implies the unsatisfactoriness as produced by the vicissitude-potentiality, which is the nature of all conditioned phenomena.

The Buddha does not deny happiness in the ordinary sense of the word when he speaks of dukkha as an inherent characteristic of things and necessary condition of life. Nor does he advocate an asceticism whereby we have to avoid all pleasures by closing our eyes and ears and pretending to be blind and deaf to all objects around us.

The Buddha, however, wants those who experience such pleasures to realize their limitations and impermanent nature. In Anguttara Nikaya, he refers to happiness based on the senses and spiritual bliss which is independent of material things or sensual desires. The first is the happiness of sense pleasures and the other, of renunciation. But all these are included, in their ultimate sense, in dukkha.

The second category of dukkha is designated viparinama-dukkhata, being characterized by impermanence, transiency and ephemerality.

The third form of dukkha, which is rcognized in inherent liability to sufferings as a result of conditionality in all existential phenomena, is the most important aspect of the first Truth. It is identified with the Five Aggregates, namely, Corporeality, Sensation, Perception, Mental Formations, and Consciousness, that constitute an "individual", the object of primordial attachment, and "I" or "being".

Greed, desire, and attachment are the sources of dukkha. We feel unhappy, disappointed, and depressed because we are attached to ourselves or our identities. Everything that we experience is related to us and consequently causes in us the dual concepts of like and dislike, good and bad, desirable and undesirable. Our mind is thus influenced by what we experience and loses its freedom. The Buddha, therefore, says: The Five Aggregates of Attachment are dukkha.