Answer:
Prayer has both a concrete sense: There are at least two versions of the Lord's Prayer. and an abstract sense: In the absence of any proven cure we will have to rely on prayer. It seems clear to me that God (with a capital G) is a Proper Name and so a Proper Noun.
1.a devout petition to God or an object of worship. a spiritual communion with God or an object of worship, as in supplication, thanksgiving, adoration, or confession. the act or practice of praying to God or an object of worship.
[tex]i \: hope \: help \: you \infty [/tex]