ARTICLES (a/an/the)

 Jobs

When we say what people's jobs are, we usually use a/an.

He's an architect.
She's a scientist.
My grandmother was a teacher.

Singular nouns

Singular, countable nouns always have an article – a/an or the (or another determiner – my, your, this, that, etc.).

We use a/an – the indefinite article – when we talk about something for the first time, or something that is part of a group or type.

I saw a good film yesterday.
Do you want a drink?

We use a when the word that follows it begins with a consonant sound. We use an when it's followed by a vowel sound. This makes pronunciation easier.

She has a university degree.
It took me an hour to get home.

We use the – the definite article – when the listener already knows which thing we are talking about because it was mentioned before or because there's only one of them.

I'm going to take the dog for a walk.
Have you seen the car key?
They go to the school next to the bridge.

Things in general

When we talk about things in general, we normally use a plural or uncountable noun with no article.

Birds eat worms.
Water freezes at 0°C.
Children need a lot of sleep.

Particular groups of things

When we talk about a particular group of things, we use the.

We went to the zoo and saw the kangaroos. (These are the particular kangaroos in that zoo – not kangaroos in general.)

Common phrases

We don't usually use an article in expressions with bed, work and home.

go to bed / be in bed
go to work / be at work / start work / finish work
go home / be at home / get home / stay at home

We also don't normally use an article in expressions with school, university, prison and hospital.

start school / go to school / be at school
go to university / be at university
be sent to prison / go to prison / be in prison
go to hospital / be in hospital

But we usually use the if someone is just visiting the place, and not there as a student/prisoner/patient, etc.

My son has started school now. I went to the school to meet his teacher.
I went to the prison a lot when I was a social worker.
I'm at the hospital. My sister has just had a baby.

Place names

We don't normally use an article for continents, most countries, cities, towns, lakes, mountains or universities. So, we say:

Africa, Asia, Europe
India, Ghana, Peru, Denmark
Addis Ababa, Hanoi, New York, Moscow
Lake Victoria, Lake Superior, Lake Tanganyika
Mount Everest, Mount Kilimanjaro, Mount Elbrus
Cardiff University, Harvard University, Manchester University

Some countries are different. Country names with United have the. There are other countries which are exceptions too. So, we say:

the United Arab Emirates, the United Kingdom, the United States of America, the Bahamas, the Gambia Seas and oceans 

Mountain ranges and Rivers have the:

the Atlantic, the Pacific, the Mediterranean, the Andes, the Himalayas, the Alps, the Nile, the Amazon, the Yangtze,

Universities with of in the title also have the:

the University of Cape Town, the University of Delhi, the University of Tokyo

Incorrect : My mother is a honest woman.

Correct : My mother is an honest woman.

When the first letter of a word is a vowel but is pronounced with a consonant sound, use a

Incorrect : She is an United States senator.

Correct : She is a United States senator.

Sources : 

https://www.grammarly.com/blog/articles/

https://learnenglish.britishcouncil.org/grammar/beginner-to-pre-intermediate/articles-1

https://learnenglish.britishcouncil.org/grammar/beginner-to-pre-intermediate/articles-2