Nouns may be either single words or compounds made of two or more nouns, like football, or an adjective followed by a noun, like emotional intelligence. Compound nouns may be spelled as two words, hyphenated or combined as a single word. As long as they refer to a single thing, the words are considered a compound noun.
There are quite a few subcategories of nouns but they all fall into one of two main categories: proper nouns and common nouns. Proper nouns are official names for specific entities, places, things and concepts, which are identified as such through capitalization. Days of the week, months, place names, people’s names, official holidays and company names are among the many examples of proper nouns (which are sometimes broken down into proper nouns and proper names).
Concrete nouns identify things that have some kind of physical presence or impact that are usually detectable through one of the five senses: sight, hearing, touch, smell or taste. However, some things that humans can’t detect – carbon monoxide, for example, or a sound pitched beyond the human range of hearing, like ultrasound or (for adults) the mosquito teen repeller – are still considered concrete because they have physical presence.
Abstract nouns identify things without a physical presence, such as emotions, concepts, qualities and experiences, among other things. A few somewhat random examples include blue, bliss, love, privacy, compatibility, Cyber Monday, anthropomorphism and quantum theory.
Countable nouns are things that are identifiable as discrete units, like beans; mass nouns, on the other hand refer to things that can’t be counted, like bean dip. Pronouns are also considered a type of noun, although they are words that substitute for nouns. She, for example, is a pronoun that could be used to refer to Grace Hopper, once it had been established that was the person we were talking about.
Depending on how they are used, nouns and other parts of speech often change from one to another. Gerunds, for example are nouns that are formed from verbs with the addition of the ing prefix. In the sentence, Tweeting is an important part of my job, tweeting is a gerund. However, in another sentence, such as I was tweeting about gerunds, tweeting is a different part of speech known as a present participle.