ARTICLES WITH SINGULAR, PLURAL AND UNCOUNTABLE NOUNS
The first time you mention a singular countable noun, the correct article is usually a or an (unless there is only one of that noun or you expect readers to already know which one). When you refer to that noun again, you should use the.
There is a new building behind our school. I think the building is going to be a convenience store.
When you are referring to specific examples, use the before a plural noun. When you are writing about those items in general, you don't need an article.
Animal names, when referring to that animal in general, can be singular with the or can be plural.
Most other countable nouns can also be singular or plural when they are referred to in general, but most should have a or an, not the, when they are mentioned the first time.
Sometimes, writers have three choices:
Look at these sentences, which refer to uncountable nouns (in bold type). You'll see that the rule is similar to the rule for singular nouns, but you can't use a or an. The first time you mention an uncountable noun, you might want to use an amount such as "some."