Merriam-Webster's Collegiate® Dictionary, 11th Edition
PRAYER
I. noun
Usage: often attributive
Etymology: Middle English, from Anglo-French priere, praiere, preiere, from Medieval Latin precaria, from Latin, feminine of precarius obtained by entreaty, from prec-, prex
Date: 14th century
1. a. an address (as a petition) to God or a god in word or thought , a set order of words used in praying, an earnest request or wish, the act or practice of praying to God or a god , a religious service consisting chiefly of prayers, something prayed for, a slight chance ,
II. noun
Etymology: Middle English prayere, from prayen to pray + 2-er
Date: 14th century
one that prays ; supplicant