In folk belief, spirit is the vital principle or animating force within all living things. As far back as 1628 and 1633 respectively, both William Harvey and René Descartes speculated that somewhere within the body, in a special locality, there was a 'vital spirit' or 'vital force', which animated the whole bodily frame, just as the engine in a factory moves the machinery in it. Spirit has frequently been conceived of as a supernatural being, or non-physical entity; for example, a demon, ghost, fairy, or angel. In ancient Islamic terminology however, a spirit (r), applies only to pure spirits, but not to other invisible creatures, such as jinn, demons and angels.
The concepts of spirit and soul often overlap, and both are believed to survive bodily death in some religions, and "spirit" can also have the sense of ghost, i.e. a manifestation of the spirit of a deceased person. Spirit is also often used to refer to the consciousness or personality.
A distinction between soul and spirit also developed in the Abrahamic religions: Arabic nafs () opposite r (); Hebrew neshama ( nâmâh) or nephesh (? nép?e?) (in Hebrew neshama comes from the root N?M or "breath") opposite ruach ( rúa?). (Note, however, that in Semitic just as in Indo-European, this dichotomy has not always been as neat historically as it has come to be taken over a long period of development: Both ? (root ?) and (root ), as well as cognate words in various Semitic languages, including Arabic, also preserve meanings involving miscellaneous air phenomena: "breath", "wind", and even "odour".)
Christian Science uses "Spirit" as one of seven synonyms for God, as in: "Principle; Mind; Soul; Spirit; Life; Truth; Love"
Latter Day Saint prophet Joseph Smith Jr. taught that the concept of spirit as incorporeal or without substance was incorrect: "There is no such thing as immaterial matter. All spirit is matter, but it is more fine or pure, and can only be discerned by purer eyes." Regarding the soul, Joseph Smith wrote "And the Gods formed man from the dust of the ground, and took his spirit (that is, the man's spirit), and put it into him; and breathed into his nostrils the breath of life, and man became a living soul." Thus, the soul is the combination of a spirit with a body (although most members use "soul" and "spirit" interchangeably). In Mormon scripture, spirits are sometimes referred to as "intelligences". But other Mormon scriptures teach that God organized the spirits out of a pre-existing substance called "intelligence" or "the light of truth". While this may seem confusing, it can be compared to how a programmer writes an algorithm by organizing lines of logical code. The logic always existed, independent of the programmer, but it is the creator who organizes it into a living spirit / intelligence / soul.
Various forms of animism, such as Japan's Shinto and African traditional religion, focus on invisible beings that represent or connect with plants, animals, or landforms (kami): translators usually employ the English word "spirit" when trying to express the idea of such entities.
According to C. G. Jung (in a lecture delivered to the literary Society of Augsburg, 20 October 1926, on the theme of "Nature and Spirit"):
The connection between spirit and life is one of those problems involving factors of such complexity that we have to be on our guard lest we ourselves get caught in the net of words in which we seek to ensnare these great enigmas. For how can we bring into the orbit of our thought those limitless complexities of life which we call "Spirit" or "Life" unless we clothe them in verbal concepts, themselves mere counters of the intellect? The mistrust of verbal concepts, inconvenient as it is, nevertheless seems to me to be very much in place in speaking of fundamentals. "Spirit" and "Life" are familiar enough words to us, very old acquaintances in fact, pawns that for thousands of years have been pushed back and forth on the thinker's chessboard. The problem must have begun in the grey dawn of time, when someone made the bewildering discovery that the living breath which left the body of the dying man in the last death-rattle meant more than just air in motion. It can scarcely be an accident onomatopoeic words like ruach (Hebrew), ruch (Arabic), roho (Swahili) mean 'spirit' no less clearly than (pneuma, Greek) and spiritus (Latin).
Similar concepts in other languages include Greek pneuma, Chinese Ling and hun () and Sanskrit akasha / atman (see also prana). Some languages use a word for spirit often closely related (if not synonymous) to mind. Examples include the German Geist (related to the English word ghost) or the French l'esprit. English versions of the Bible most commonly translate the Hebrew word ruach (; wind) as "the spirit." 
Alternatively, Hebrew texts commonly use the word nephesh. Kabbalists regard nephesh as one of the five parts of the Jewish soul, where nephesh (animal) refers to the physical being and its animal instincts. Similarly, Scandinavian, Baltic, and Slavic languages, as well as Chinese (? qi), use the words for breath to express concepts similar to "the spirit".
^Chodkiewicz, M., "Rniyya", in: Encyclopaedia of Islam, Second Edition, Edited by: P. Bearman, Th. Bianquis, C.E. Bosworth, E. van Donzel, W.P. Heinrichs. Consulted online on 18 November 2019 doi:10.1163/1573-3912_islam_SIM_6323
First published online: 2010
^Burtt, Edwin A. (2003). Metaphysical Foundations of Modern Physical Science. Mineola, New York: Dover Publications, Inc. p. 275.
^OED "spirit 2.a.: The soul of a person, as commended to God, or passing out of the body, in the moment of death."
^an?-, from *?2en?1-. Watkins, Calvert. 2000. The American Heritage Dictionary of Indo-European Roots, second edition. Boston: Houghton-Mifflin Co., p. 4. Also available online. (NB: Watkins uses ?1, ?2, ?3 as fully equivalent variants for h1, h2, h3, respectively, for the notation of Proto-Indo-European laryngeal segments.)
^Koehler, L., Baumgartner, W., Richardson, M. E. J., & Stamm, J. J. (1999). The Hebrew and Aramaic lexicon of the Old Testament (electronic ed.) (711). Leiden; New York: E.J. Brill.
^Brown, F., Driver, S. R., & Briggs, C. A. (2000). Enhanced Brown-Driver-Briggs Hebrew and English Lexicon (electronic ed.) (659). Oak Harbor, WA: Logos Research Systems. (N.B. Corresponds closely to printed editions.)[ISBN missing]
^Brown, F., Driver, S. R., & Briggs, C. A. (2000). Enhanced Brown-Driver-Briggs Hebrew and English Lexicon (electronic ed.) (924ff.). Oak Harbor, WA: Logos Research Systems. (N.B. Corresponds closely to printed editions.)[ISBN missing]