Hello, fellas. In this session we will learn how to use a or no article. A or no article is used when a speaker is making a generalization.
A comes before a singular noun when a generalization is expressed.
1) A leaf is green.
2) A cat makes a good pet.
In the above-mentioned examples, the speaker is talking about any leaf and any cat, all leaves and all cats, leaves and cats in general.
No article is used when a speaker is making a generalization with a plural count noun.
3) Leaves are green.
4) Cats make good pets.
The meaning of these examples is similar to that of example 1 and 2. Sometimes an expression of quantity (e.g., almost all, most, some) is used in a generalization.
5) She saw some cats in her room.
6) Most students read books.
If a generalization is about an uncountable noun, no article is used.
7) Milk is good for your health.
8) Fruit contains vitamins.
Some can be used in the generalization of an uncountable noun.
9) Can you get me some food?
10) He drank some milk.
Betty Schrampfer Azar, Fundamentals of English Grammar: Third Edition