You may have already guessed it, but I’m talking about nouns, not behavior. A common noun would be park. A proper noun would be Yellowstone National Park.
Much to my surprise, Merriam-Webster had a definition:
: a word or group of words that is the name of a particular person, place, or thing and that usually begins with a capital letter
Here are a few more examples off the top of my head: Grandma Betty, Mitch Romney, Skyline High School, Skippy, Boise, Round-Up, and Palm Beach International Airport.
But what about common nouns?
: a word that refers to a person, place, or thing but that is not the name of a particular person, place, or thing
This would include: schools, grandmothers, dogs, airports, governors, capital cities, weed killers, and so on.
Need an easy trick to figure out whether to capitalize a noun? Think: Is there only one of this person, place, or thing or more than one? If only one, capitalize; if not, lowercase.
Have any examples of tricky-to-identify nouns? Leave them in the comments, so we can discuss!