- The definite article (the)
1. When the listener or reader knows which noun we are talking about either because it has been mentioned before or it is clear which one.
→ There is a new employment law on retirement ages. In my opinion, the law is unfair.
→ I think the government needs to renew its economic policy.
2. When the speaker or writer qualifies a noun with information to make it definite.
→ You know the minister who was sacked because he was taking bribes.
3. When there is only one of something.
→ The world is suffering from this economic downturn.
4. With ‘… of …’ and ‘… of a …’ (for definite noun phrases).
→ The rate of inflation is rising.
→ I noticed the papers of a fellow commuter on the train.
5. With superlatives, with geographical features and weather, and with well – defined groups.
→ He is the hardest working employee in the company.
→ I could not get to work because of the fog.
→ The bankers have put this country into a state of crisis.
- The indefinite article (a/an)
1. When the listener or reader does not know the person or thing we are referring to because this is mentioned for the first time or is unspecific or unimportant.
→ There is a new employment law on retirement ages.
→ We need an assistant.
2. When an adjective comes before a singular noun.
→ High taxation on the rich is a very unfair system.
3. When mentioning a quantity such as a fraction or a number to mean “one”.
→ a third, a million, a hundred.
4. When we talk about one member of a group or class.
→ An employer must be aware of employment law. (Any employer)
→ He is a banker. (One of a job type)
1. When we refer to a noun in general (this is common in academic writing). Usually, the noun is in the plural form.
→ Jobs are essential if you want to make money.
2. With uncountable nouns, when the noun is not a specific group.
→ Jobs are essential if you want to make money.
→ Economics is an essential part of politics.
3. With most proper nouns (names).
→ She works for Google.
→ I have another bank account in Switzerland.
NOTE: These rules cover most article usage, but as so often in grammar, there are exceptions.