Definition:
Vitre is the third of the Four Core Notions, and bears no English equivalent. The best translation would be "that which facilitates spirituality".
What this means is that vitre refers to any practice which helps prepare the ardt of the spiritual practitioner. It is the processes which help the practitioner get into the right mindset and headspace to do their spiritual practice, whether that practice be prayer, meditation, or something else.
It is the preparation of the environment around us as well as within us to engage with spiritual praxis.
It is facilitating spirituality.
Etymology:
The Kibtisk word which vitre comes from is 'vutera', meaning 'water'.
This is due to the rain-like nature vitre has: it softens the earth (ardt) and waters the seeds planted therein. It is a nurturing and gentle element which has a lasting effect, as do spirituality and its facilitation (i.e. vitre).
In other words, the facilitating of spirituality softens the inner-self to receive the benefits of the spiritual practice being facilitated. Vitre is like the rain which falls on the earth.
Similarly, the words 'spirit' and therefore 'spirituality' in Kibtisk (vótrhie and vótrhiskhet) find their root in the word for 'water' (vutera). If vitre is the rain then vótrhiskhet is the river. If facilitating spirituality brings water into the ardt, spirituality itself is the river flowing through the ardt.
Explanation:
Due to the Core Notion of the ardt and the role it plays in the Two Principles of the yürna and baden, vitre as something which has a beneficial effect on the ardt also becomes a vital component to the practice of the Kibtisk Way.
The intentional practice of vitre in order to facilitate the wider spiritual practices available to us then becomes one of the key Kibtisk Practices known as vitren.
The virtue of practising vitre is that it softens the ardt, making us soft-hearted and gracious, allowing us to project (ütbaden) this virtue onto others. This virtue is known as zeva (graciousness; soft-heartedness), and is one of the Kibtisk virtues which followers of the Kibtisk Way aim to emulate.
Vitre therefore is a Core Notion due to its effect on the ardt and its wider contribution to what we baden and how we journey through our yürna.