2. Articles
When a thing is unfamiliar or mentioned for the first time, it gets the indefinite article a or an in front of it.
The article a is used when the first letter of the word is pronounced as a consonant: a car, a pony, a tree.
The article an is used when the first letter of the word is pronounced as a vowel: an accent, an egg, an idea.
Note! Words that begin with a vowel will also get the article a if the vowel is pronounced as a consonant: a university, a user.
When the thing is already familiar or has been mentioned before, it gets the definite article the in front of it:
We have a cat and a dog, and sometimes the dog chases the cat.
Sometimes neither article is used, for example, when something is discussed in a general sense:
There are dogs in the park.
But:
Those are the dogs that bark at night.
Names of people, places, days of the week, months and holidays don’t get an article:
Mikko met Hanna in Sweden in July,
not Mikko met the Hanna in a Sweden in the July.