a / an — indefinite article

Use a/an with singular countable nouns. Use an before vowel sounds (not just vowel letters).

UseExample
First mention — introducing something newI saw a dog in the park.
One of many — not a specific oneCan you pass me a pen?
Jobs and rolesShe is a teacher. He works as an engineer.
Before vowel sound → anan apple · an hour · an MBA · a university (sounds like "yu")

the — definite article

Use the when the speaker and listener both know which specific thing is meant.

UseExample
Second mention — already introducedI saw a dog. The dog was barking.
Unique things (only one exists)the sun, the moon, the internet, the sky
SuperlativesShe is the best student in the class.
Specific geographical featuresthe Amazon, the Alps, the Pacific Ocean
Ordinal numbersthe first, the second floor

Zero article — no article

Use no article (zero article) in these common situations:

UseExample
Plural/uncountable nouns in generalDogs are loyal. Water is essential.
Countries, cities, continents (most)I live in Spain. She's from Paris.
LanguagesShe speaks Japanese.
Sports and gamesHe plays football.
MealsWe had dinner at eight. (but: "a nice dinner")
Institutions used for their purposeShe's in hospital. He goes to school. (UK English)
the + countries: Use "the" with plural or descriptive country names: the USA, the UK, the Netherlands, the Philippines, the Czech Republic.

Exercises

Choose the correct article (or Ø = no article).

1. She is ___ architect. (profession)

2. I bought a new phone. ___ phone has a great camera.

3. ___ gold is more expensive than silver. (general statement)

4. ___ Amazon is the longest river in South America.

5. She loves playing ___ tennis every weekend.