The letter U, through its connection with Vaiśvānara, advances toward stability. The explanation of U is its condition of Taijasa.

U — the second letter of Oṃ — corresponds to the dream state (svapna), represented by Taijasa.

Ukāra: the sound U. Phonetically, the transition from A to U implies an inward movement — the tongue moves backward, the resonance becomes more closed. It is not a total opening like A, but a movement within.

Pratiṣṭhā (stability, foundation): U is not an abandonment of A but a deepening. Waking (A) finds its foundation in the subtle world of dream (U). What in waking appears as external world, in dream appears as internal world — the same reality, seen from another level.

Taijasatvam: the quality of Taijasa, the luminous. The inner fire (tejas) that illuminates dreams. It is not physical light but the light of consciousness turning back upon itself.

The transition A → U reflects the movement of meditative practice: from external world (waking) to internal world (dream). In yoga nidrā and visualization practices, this transition is trained consciously.

The word upavyākhyāna (explanation, interpretation) appears again — each letter of Oṃ is not just a sound but a map of consciousness.