Patanjali's yoga sutras

svapnanidrājñānālambanaṃ vā || 1.38 ||

svapna https://www.wisdomlib.org/definition/svapna

Source: Namah, the Journal of Integral Health: Hinduism

The word ‘svapna’ has two meanings in Sanskrit: sleep and dream. Svapna (as sleep) is one of the three sub-pillars of life and detailed descriptions of it have been made in the Classics. Svapna (as dream) is a series of happenings which evolve in various stages of sleep. It is used as a diagnostic and prognostic tool in Āyurveda. A clinical analysis of dream, in Ayurvedic and classical literature, is the subject matter of this article.

The primary meaning of the word svapna is sleep. Nidrā, śayana, svāpa, svapna, sṃaveśa are synonyms. The word svapna has been used in the ‘sleep’ sense in different places in various texts . Its secondary meaning is ‘the subject’s’ experience in the different state of sleep, which is mentioned in various contexts and instances in the Caraka saṃhitā 

Source: Wisdom Library: Maha Prajnaparamita Sastra

Svapna (स्वप्न, “dream”) refers to one of the ten comparisons (upamāna) according to the 2nd century Mahāprajñāpāramitāśāstra chapter 11. These upamānas represent a quality of the Bodhisattvas accompanying the Buddha at Rājagṛha on the Gṛdhrakūṭaparvata. They accepted that dharmas are like a dream (svapna). There is no reality in a dream but nevertheless we believe in the reality of the things seen in a dream. After waking up, we recognize the falsity of the dream and we smile at ourselves. In the same way, the person deep in the sleep of the fetters (saṃyojana-nidra) clings to the things that do not exist; but when he has found the Path, at the moment of enlightenment, he understands that there is no reality and laughs at himself. This is why it is said: like in a dream (svapna).

Tibetan Buddhism (Vajrayana or tantric Buddhism)

[«previous (S) next»] — Svapna in Tibetan Buddhism glossary

Source: WikiPedia: Vajrayana

Svapna (स्वप्न) or Svapnadarśana refers to the “Yoga of the dream state” and represents one of Nāropa’s Six Dharmas (ṣaḍdharma) in Tibetan Buddhist Tantric practices .—In the Yoga of dreaming (rmi lam, *svapna), the Yogi learns to remain aware during the states of dreaming (i.e. to lucid dream) and uses this skill to practice Yoga in the dream.

Merrily merrily merrily merrily life is but a dream.