Should words be capitalized for being religious terms?
Not necessarily. It depends on whether they’re considered proper names.
For example, church, communion, atheist, agnostic, and spirituality are not proper names because they’re not recognised entities.
In contrast, the Church of England is a proper name because it refers to an institution and should therefore be capitalised. However the church is not capitalised when you’re simply referring to a building rather than to the institution itself.
Holy Communion should be capitalised as a proper name; however, communion used as a general term should not be, because it isn’t a proper name.
Capitalization (especially of titles) is a tricky business in English. There is no hard-and-fast rule about capitalization. In fact, many of the major style guides disagree on exactly what should or shouldn't be capitalized. However, I'll give some general guidelines and let you make up your own mind:
Titles in direct address
In all major style guides, when a title is used as a name in direct address of that individual, it is capitalized. For example: "That was very kind of you Mom." "I love you Dad." "Stop being so good to me, Master." "So, I have to have surgery, Doctor?"
Titles used in direct reference
When referring to a specific individual with their title, the title should be capitalized. For example: "I was excited when President Barrack Obama walked in the room." "My favorite comic book character is Mr. Tony Stark." "It took a while, but we finally got in to see Doctor John Smith."
However, (somewhat less commonly) some prefer that occupational titles not be capitalized, unless abbreviated. For example, "Dr. John Smith" and "doctor John Smith".
Titles used in indirect reference
Most style guides prefer titles used in reference to be lowercase. For example, "I love my mother." "The president gave a great speech." "My doctor did a great job with my surgery."
However, some titles are exempted from this. God (when referring to the Judeo-Christian god) is always capitalized. The King and the Queen are often capitalized. (For example, "The Queen has quite a way with words.") When referring to a specific office, there is disagreement about what should or should not be capitalized. Chicago and Wikipedia prefer "the president of the United States", while NY Times prefers "the President of the United States". However, everyone prefers "King of France" to "king of France".
Best Answer
There doesn't seem to be a hard and fast rule.
• An Ngram comparison shows that "River Basin" is more common in American English but "river basin" is more common in British English.
• Alaska's very through guide to capitalization of geographic terms recommends lower case for compound nouns like "river basin", "river mouth", etc. but capitals when it's just the river's proper name – so "Yukon River" but "Yukon river basin".
• The Chicago Manual of Style (section 8.53) uses "River" in caps as part of the proper name but "basin" in lowercase because it's a modifier: the Mississippi River valley, the Amazon basin, the Mississippi delta.