A colleague of mine and I created a set of grammar materials when we taught high school. This is an excerpt:
GENERAL STATEMENTS
A general statement is a statement about a category of items in the world. When making a general statement, we do not use an article at all.
- With plurals
When we say, for example, I love dogs, we are making a general statement about a category of animal. When we say, I hate vegetables, we are again making a general statement about a food category. Both of these sentences are general statements with plurals; dogs is a plural noun and vegetables is a plural noun, and we are not referring to any specific dogs or vegetables. We are referring to the category of dogs and vegetables. Thus, we do not use an article.
EXAMPLES OF GENERAL STATEMENTS WITH PLURALS
Cats are unfriendly.
There are too many cars on the road.
There are pencils for sale at the store.
I love to put posters on my wall.
*** o With uncountables**
We also make general statements with uncountable nouns. When we say, I love music, we are making a general statement with an uncountable noun, music. When we say, I hate homework, we are making a general statement with the uncountable noun, homework. In both cases, we are not referring to any specific music or homework so they are considered general statements with uncountables. We, therefore, do not use an article.
EXAMPLES OF GENERAL STATEMENTS WITH UNCOUNTABLES
Information is available at the library.
Pollution is destroying the earth.
Homework is boring.
SPECIFIED PLURALS AND UNCOUNTABLES
We use the when we have specified the plural or uncountable. In other words, use the when we know exactly which item(s) or object(s) we are discussing.
*** o Specified plurals**
When we say, I love the movies made by Steven Spielberg, we use the because we know which movies. They are the movies made by Steven Spielberg. When we say, the police officers in Richmond are very professional, we use the because we have specified which police officers.
EXAMPLES OF SPECIFIED PLURALS
The boats in Vancouver Harbour are protected from storms.
I like to visit the whales in the aquarium.
Many people like the activities available in Vancouver.
The courses offered at UBC are numerous and varied.
Specified uncountables
When we say, the homework from Math class is easy, we have used the because we have specified which homework. It is the homework from Math class. When we say, the pollution created by the local pulp mill is making people sick, we have used the, because we have specified which pollution. It is the pollution created by the local pulp mill.
EXAMPLES OF SPECIFIED UNCOUNTABLES
The vocabulary from English class seems easy, but it's not.
The information that I received from the government is useful.
The ice-cream made by my friends is always good.
I want to see the jewelry that my friend bought yesterday.
Note: Never use a or an before a plural or an uncountable noun.
SINGLE UNSPECIFIED NOUNS
When we have one item, and we cannot identify and thus specify it, we use a or an in front of it. This is a general statement with a single unspecified noun. When we say, I want to buy a cat, we use a because there is only one cat, and we do not know which cat. In this case, the word cat is a single unspecified noun. When we say, I would like a bike, we use a because there is only one bike, and we do not know which bike it is. In other words, bike is a single unspecified noun. Single unspecified nouns are preceded by a or an.
EXAMPLES OF SINGLE UNSPECIFIED NOUNS WITH “A” OR “AN”
There is a cat on the road.
A dog is difficult to care for.
May I have a drink please?
I do not have a pen.
Please bring me a tissue.
SINGLE SPECIFIED NOUNS
When we know exactly which single item we are talking about, it is specified, and we use the in front of it. When we say, the dog that lives next door barks all of the time, we know exactly which dog it is; when we say, I bought the car that John used to own, we know exactly which car it is. Hence, we must use the before the specified noun.
The pen on the floor is mine.
The movie that is playing at 10 pm is sold out.
The car that is parked under the street lamp is Jack’s.