Written by furious kitten
Most nouns in English are not capitalized. When they are proper nouns, we do capitalize them. Proper nouns refer to specific people, places, or things. For example, we would leave the word city lowercase but capitalize a specific city, such as Seattle or Forks.
A great example of this is the difference between a type of person and a specific person. If you want to write about being a leader in general, you would write that you see someone being a president of a company someday. Referring to a specific position, however, becomes a proper noun. Obama is the President of the United States. This also explains why we capitalize people’s names, such as Bella and Edward, versus woman and man. Groups of words are also capitalized when used as a name. In the Harry Potter series, J.K. Rowling always capitalized You Know Who and He Who Must Not Be Named when referring to Voldemort.
Continuing with names, when nouns are used as a name they are capitalized. That explains the following sentence, “My mom would never let me call her by her first name; she always insists we call her ‘Mom’”. Mom is not capitalized in the first instance because it is being used as a common noun. It is capitalized in the second instance because it is used as a direct address. Titles are also capitalized, such as Dame Judi Dench and Chief Swan.
The same rule applies for god versus God. The lowercase form is used in a general sense. We capitalize God when we use it to refer to a specific deity. When speaking about Christianity in English, we use the same word for both a deity and our specific deity, but it helps to think of the latter as a name (which it is). “Oh, God, I can never remember any of the Greek gods besides Zeus and Athena.” See what I did there? The first God is capitalized because it invokes the singular and specific Christian deity, but the second is lowercase because it just refers to a type of person. Zeus and Athena are capitalized because they are specific gods, and also names.
Some people may try and argue that phrases such as “Oh my God” have become so commonplace that they are disassociated from religion and therefore you do not need to capitalize God. Eh, I don’t buy it. The phrase originated in a religious context, and for most people still has the same meaning. You may be able to get away with a lowercase god in fanfic, but it wouldn’t fly in more formal settings.
As I mentioned in the first paragraph, specific place names are capitalized. This also goes for adjectives that pertain to locations, as in my sentence above about Greek gods. I am talking about gods from the ancient civilization in Greece (a specific country), so I also capitalize the adjective Greek. The same goes for Italian leather, Chinese food, and French wine.
Things are capitalized when they refer to a specific type (see a pattern here?). With things, this often means brand names. I buy a box of tissues (general), but a box of Kleenex (specific brand). I usually only see this done incorrectly when brands have become household names, such as Kleenex or Ziploc.
A few other examples of things as proper nouns: Time periods are considered proper nouns, such as the Great Depression (versus saying that Edward suffers from depression). Some people capitalize Earthearth when they mean the ground beneath our feet. Style guides differ on this, though, so there’s no hard and fast rule. Lastly, we’ll talk about subject names. Take this sentence: “Edward always excelled in math, so he decided to take the Advanced Mathematical Modeling class.” In the first instance, math is not capitalized because it refers to a general subject area. It would be capitalized in the second instance because it is part of a specific course name, which is capitalized like other titles. when they are referring to the planet in a solar context, versus
Nouns are capitalized when they are considered proper nouns and written in lowercase when they are common nouns. To tell the difference, ask yourself, “Is this noun referring to a general type, or is it referring to something specific?”