A noun can be a person, place, thing, entity or idea, but a proper noun is even more specific. It gives the actual name of the person, place, or thing. There are usually certain words that you’ll always be able to identify as a proper noun, including countries and cities, months, days of the week, names of companies or organizations, honorary titles, and names of people or even pets. Unlike the common noun, the proper one is indicated by a capital letter at the beginning of each word.
Though it’s fairly easy to remember that certain things like the names of the countries or the name of person will begin with a capital letter, there are a few times when people can forget they are using a proper noun. This is especially the case when you are addressing someone that you call by a common noun. For instance if you refer to you mom as “Mother,” when you use this in written form, the word would be capitalized. This may be a bit hard to understand but actually in this sense “Mother” becomes a name for your mom, very much like her personal name.
Consider the following examples:
“I am going to the store with my mother.”
“Would you like to go to the store with me, Mother?”
In the first instance, you are using the term in a general way, though it’s pretty clear you’re speaking of your mother. In the second example, you use the term as a title and a name, so that the noun becomes a proper noun instead of a common one.
Other types of proper nouns that may be a little hard to remember include things like names of companies. In most cases, unless the company specifically uses a lowercase start in their title, many names of companies will be capitalized. You should check with a company website if you have any doubts regarding this.
If you say, “That company is really responsible” it is not the same as saying “Google is really responsible.” Just remember that proper noun usage tends to mean you have named the thing you are talking about in the most specific way possible.
One type of common noun that tends not to ever become a proper noun is the category of ideas. So for example things like “knowledge,” “intelligence” “love,” or “kindness” are not proper nouns though they can seem like pretty specific terms. Of course the other thing to bear in mind is that all nouns, common or proper, will have their first letter capitalized if they are the beginning word in a sentence.