Most major religions in the world involve prayer in one way or another in their rituals. Although in many cases the act of prayer is ritualized and must be followed through a sometimes strict sequence of actions (even going as far as restricting who may pray), other religions, mainly the Abrahamic religions, teach that prayer can be done spontaneously by anyone at any moment.

Scientific studies regarding the use of prayer have mostly concentrated on its effect on the healing of sick or injured people. The efficacy of petition in prayer for physical healing to a deity has been evaluated in numerous studies, with contradictory results.Galton F. Statistical inquiries into the efficacy of prayer. Fortnightly Review 1872;68:125-35. Online version.Byrd RC, Positive therapeutic effects of intercessory prayer in a coronary care unit population. South Med J 1988;81:826-9. PMID 3393937.Harris WS, Gowda M, Kolb JW, Strychacz CP, Vacek JL, Jones PG, Forker A, O'Keefe JH, McCallister BD. A randomized, controlled trial of the effects of remote, intercessory prayer on outcomes in patients admitted to the coronary care unit. Arch Intern Med 1999;159:2273-8. PMID 10547166.O'Laoire S. An experimental study of the effects of distant, intercessory prayer on self-esteem, anxiety, and depression. Altern Ther Health Med 1997;3:38-53. PMID 9375429. There has been some criticism of the way the studies were conducted.Benson H, Dusek JA et al. "Study of the Therapeutic Effects of Intercessory Prayer (STEP) in cardiac bypass patients: a multicenter randomized trial of uncertainty and certainty of receiving intercessory prayer." American Heart Journal. 2006 April; 151(4): p. 762-4.http://www.infidels.org/library/modern/gary_posner/godccu.html A critique of the San Francisco hospital study on intercessory prayer and healing - Gary P. Posner, M.D.

Etymology

Pray entered Middle English as preyen, prayen,and preien around 1290, recorded in The early South-English Legendary I. 112/200: And preide is fader wel latinx: ȝerne, in the sense of "to ask earnestly." The next recorded use in 1300 is simply "to pray." The word came to English from Old French preier, "to request" (first seen in La Séquence de Ste. Eulalie, ca. 880) In modern French prier, "to pray," the stem-vowel is leveled under that of the stem-stressed forms, il prie, etc. The origin of the word before this time is less certain. Compare the Italian Pregare, "to ask" or more rarely "pray for something" and Spanish preguntar, "ask."