Remember that we’ve said the Buddha uses dukkha to refer to ordinary suffering and in deeper way to suggest a basic unsatisfactoriness pervading all existence. Let’s look at both of these.

Ordinary suffering

The Buddha explains this truth by listing various types of Dukkha.

Birth, old age, sickness and death can be thought of as occasional dukkha, since they only come at certain times.

Birth
Birth here refers to the entire period of gestation from the time of conception to exit from the womb. Birth itself is a traumatic and dramatic experience, being thrust out from the womb, being thrown out into the world. And birth is the starting point for all other forms of Dukkha that will follow during the course of life. 

Ageing
When ageing sets in, the skin wrinkles, the teeth begin to fall out, sense faculties loose their sharpness, hair turns gray, memory fades  and vitality declines.

Disease
Sickness whether physical or mental is suffering.

Death
At the end comes death. The break up of the body, the extinguishing of the life force is suffering.

The Buddha sites five terms which give a kind of overview of the vocabulary of suffering;

Sorrow is intense woe because of some deprivation.

Lamentation is crying and weeping.

Pain is bodily pain.

Grief is any kind of mental unhappiness.

Despair is the lowest point of mental anguish, when all hope is given up.

The following are referred to as frequent dukkha because we meet them quite often in life:

Union with the unpleasant  
Facing, against our will, the various unpleasant situations and disagreeable people we don't want to face is suffering.

Separation from the pleasant
We want to cling or hold to pleasant and agreeable situations or relationships we hope will last. But events follow their own law, they don’t conform to our will, and eventually these do not endure. Facing separation from these pleasant situations or people is suffering.

Not getting what we desire
Primarily we desire pleasure, wealth, fame and praise, but instead we often meet with pain, poverty, dishonor and blame. When we want to remain young, we grow old. When we want to remain healthy we fall sick. We would like to live forever but we must die. All this is suffering.

The five aggregates

All our experience, the Buddha concludes, is included in dukkha. Our psychophysical organism can be broken down into five types of factors, the basic components of our experience: material form, feeling, perception, mental formations and  consciousness.

Material form covers the physical body with its sense faculties, while the other four encompass the mental side. They are all included in Dukkha because they are all impermanent, changing from moment to moment. In fact they are only momentary events without any inner core.

What we call "my self" is just a combination of these five insubstantial aggregates changing from moment to moment.

It is the aggregates that are born, that grow old, fall sick and finally die.

Levels of Dukkha

To make it clear that Dukkha goes beyond ordinary suffering, the Buddha orders Dukkha into three levels:

Dukkha as ordinary suffering

Dukkha due to change

At a level removed from felt suffering we see that all pleasant experiences are dukkha because they are subject to change.

Dukkha points to the gap between the ideal state of permanent happiness
we so much desire, and the stumps and thorns living experience invariably throws beneath our feet.

The objects that give us pleasure are impermanent, they don’t last. And therefore the pleasure we get from them are also impermanent — it has to pass away.  When the objects of attachment pass away, because we cling to them and become attached to them the result for ourselves is pain and suffering.

Beyond this, the pleasant experiences themselves and the things that give pleasure are already Dukkha, even while we are enjoying them. Because they are bound to and will pass away, even in the immediacy of enjoyment  they are dukkha. Health can be undermined by disease and therefore even when we are healthy, the state of health is dukkha. Youth has to give way to old age. Therefore our youthfulness is still Dukkha, unsatisfactory. And life has to end in death and therefore life itself becomes dukkha.

The Dukkha of Conditioned Formations

The five aggregates (conditioned formations) of clinging are dukkha. Our individuality is simply a combination of conditioned phenomena and all conditioned phenomena are impermanent and undergo constant transformation. As a result we have no mastery over them, we have no control over them, they go their way. Because they’re in this constant process of rising and falling, for one with wisdom they are experienced as dukkha.

Is Buddha a pessimist?

The aim of the first noble truth is seeing clearly our situation, the first step on the path to liberation.

The teaching of the First Noble Truth often arouses a certain degree of emotional resistance. This has given rise to misunderstanding that Buddha was a pessimist, a negativist. We have to understand the intention of the Buddha in teaching the First Noble Truth, his aim being to lead us to liberation out of an unsatisfactory situation of Dukkha.

In coming to the Dharma we have to come with an open mind, ready to see things objectively, to see know them as they are. This calls for effort and causes some amount of internal friction. We set up emotional screens around us so that we can see and understand things in ways that are dictated by our desires, in ways that confirm our preconceptions.

But the approach required in understanding the Dhamma is quite different. The Dhamma goes against  our ordinary inclinations.

Since the Dhamma is truth we have to be prepared to look at existence as it is. For it is only by seeing and seeing rightly, that we can win freedom.  For this we have to stop seeing what we want to see and look at things objectively.

Seeing our existence from three views

To gain a complete view of our existence we have to look at life from three angles.

Enjoyment or satisfaction
Life, the Buddha teaches, involves a saga pleasure and enjoyment. Without pleasures or enjoyments in our world — belongings, relationships etc.— people wouldn't become attached to the world. It is precisely because there is enjoyment that we become attached to this world. And not all of these enjoyments are unwholesome. For example, happiness of a good family, true love, aesthetic pleasures, and the religious life can be truly gratifying.

Danger or unsatisfactoriness
However, when you look at life from angle of inadequacy you will see that since everything — including our pleasures and joys — is impermanent, hence unsatisfactory. Everything is subject to change and so at a deep level is connected with pain and dissatisfaction

Release or escape
To be free from suffering we have to examine whether the objects of enjoyment can give us complete satisfaction, recognize that it is our attachment that leads us into the suffering, and put away attachment and desire for the objects of enjoyment.

 
4

The Four Noble Truths
The First Noble Truth — Dukkha

3 of 7

Qualities of the Dharma
The Four Noble Truths
The Noble Eightfold Path
The True Nature of Existence
  The Five Aggregates of Clinging
  Anicca, Dukkha and Anatta
  Dependent Arising
  Kamma, Nibbana and Rebirth
  Kamma
  Rebirth
 

Nibbana

Meditation
The Sangha
The Buddhist Sangha