স্বপ্ন হল একটি সংস্কৃত শব্দ। হিন্দু দর্শনে স্বপ্ন হল চেতনার অবস্থা যখন একজন ব্যক্তি (সত্তা) ঘুমের মধ্যে স্বপ্ন দেখেন। এই অবস্থায় সে ইন্দ্রিয়ের দ্বারা বাহ্যিক মহাবিশ্বকে উপলব্ধি করতে পারে না। এই অবস্থায় স্মৃতি বা কল্পনার সচেতন কার্যকলাপ থাকতে পারে। এটিকে সাধারণত জাগ্রত চেতনা (জাগ্রত), গভীর ঘুমের অবস্থার সাথে তুলনা করা হয় যেখানে কোন জ্ঞান হয় না (সুষুপ্তি), এবং চতুর্থ রাজ্য যা তুরীয় নামে পরিচিত।Shiva Sutra of Vasugupta as translated by: Feuerstein, Georg (2013-09-11). The Yoga Tradition: Its History, Literature, Philosophy and Practice (Kindle Locations 9285-9291). Hohm Press. Kindle Edition. "[Even] during the differentiation [of consciousness into the three modes of] waking, dream sleep, and deep sleep, [there is continuous] emergence of enjoyment of the Fourth [i.e., absolute Reality]. (1.7) The waking state (jâgrat)  [consists in conditional or finite] knowledge (jnâna). (1.8) Dream sleep (svapna) [consists in] imagination (vikalpa). (1.9) Deep sleep (saushupta) [corresponding to] illusion (mâyâ) [consists in complete] nondifferentiation (aviveka). (1.10)"DIPAK BHATTACHARYA, THE DOCTRINE OF FOUR IN THE EARLY UPANIṢADS AND SOME CONNECTED PROBLEMS in Journal of Indian Philosophy, Vol. 6, No. 1 (September 1978), pp. 1-34. Published by: Springer. Stable URL: https://www.jstor.org/stable/23440028,Accessed: 16-12-2015 00:15 UTC "The four states are spoken of in Maitrî VII. 11.7: "He who sees with the eye, and he who moves in dreams, He who is deep asleep and is greater [than the rest]" and "These states are: - 1) waking, 2) dream sleep, 3) deep sleep (susupti), i.e. deep, dreamless sleep in which the soul becomes temporarily one with Brahman and enjoys a corresponding unsurpassable bliss, and 4) the 'fourth' state (caturtha, turya, turïya), usually called turîya, in which that disappearance of the manifold universe and the union with Brahman on which the bliss of deep sleep depends takes place not as before unconsciously, but with continued and perfect consciousness." p. 5Saraswati, Sri Swami Sivananda (2013-06-13). Kundalini Yoga (Kindle Location 2724). Kindle Edition."During the states of waking, dreaming and dreamless sleep, the Vijnana Atma which dwells in this body is deluded by Maya."Patrick Olivelle, The Early Upanishads Annotated, p. 23. "The cavity of the heart is the seat of the vital powers and the self and plays a central role in the explanations of the three states of awareness—waking, dreaming, and dreamless sleep— as well as of death. In sleep, the cognitive powers distributed throughout the body during the waking hours are gathered together in the cavity of the heart. The space of this cavity is homologized with cosmic space (see CU 3.12.7-9), and in the dream state the person travels about this space seeing and enjoying the same type of things that he experienced while awake. During deep and dreamless sleep, the self slips out of that cardiac space and enters the veins going from the heart to the peri- cardium; there it remains oblivious to everything (see BU 2.1; 4.3-4)." চেতনার এই চারটি অবস্থা ছান্দোগ্য উপনিষদে বর্ণনা করা হয়েছে।PT Raju (1985), Structural Depths of Indian Thought, State University New York Press, , pages 32-33; Quote: "We can see that this story [in Chandogya Upanishad] is an anticipation of the Mandukya doctrine, (...)"Robert Hume, Chandogya Upanishad - Eighth Prathapaka, Seventh through Twelfth Khanda, Oxford University Press, pages 268-273 মাণ্ডুক্য উপনিষদ স্বপ্নকে মনের অবস্থা হিসেবে ব্যাখ্যা করে।  তথ্যসূত্র  বিষয়শ্রেণী:হিন্দু দার্শনিক ধারণা বিষয়শ্রেণী:সংস্কৃত শব্দ ও বাক্যাংশ