Note,When preceded by the, a singular countable noun can be used to represent something as a class.
e.g. The telephone is a modern convenience.
The horse is a domesticated animal.
The eagle is a bird of prey.
In the first example, the telephone refers to telephones considered as a class. Likewise, in the other examples, the horse refers to horses considered as a class, and the eagle refers to eagles considered as a class.
A is referred to as the indefinite article because it can be used to refer to something in general terms. A and an are often used in general statements.
e.g. A bank account can provide a good means of saving money.
An accountant must have a good knowledge of arithmetic.
A good pair of scissors should be used for cutting cloth.
- The cobra is dangerous. <class>
- A cobra is dangerous. <general statement>
- An elephant never forgets. <general statement>
- The elephant never forgets. <class>