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Basic English II · Lección 09

Articles & Prepositions

Six small words that carry enormous power. A, an, and the tell your listener whether something is new or already known. In, on, and at anchor every event in time and place. Learn all six and your English becomes dramatically clearer — immediately.

A Indefinido
consonante
AN Indefinido
vocal
THE Definido
conocido
Ø Sin artículo
general
IN Período largo
área grande
ON Días / fechas
superficies
AT Hora exacta
lugar puntual
1

Articles — A / AN / THE / Ø

Los artículos indican si algo es nuevo o ya conocido para el oyente

🧠 The Master Rule

Before choosing an article, the English brain asks one single question:

The Key Question
"Can the listener identify exactly which thing I mean?"
Situation Meaning Article
The listener cannot identify which one New, unknown, first mention a / an
The listener can identify the exact thing Known, specific, unique, or already mentioned the
We talk about something in general A whole category, concept, or idea Ø (nothing)

Articles are about shared knowledge — not just grammar rules. When you say "Close the door", you use the because both you and the listener know exactly which door you mean.

The Four Articles at a Glance

A
Before a consonant sound · new info · singular countable
a book
a car · a teacher
a university*
a European city*
AN
Before a vowel sound · new info · singular countable
an apple · an egg
an idea · an office
an hour*
an honest man*
THE
Specific · known · unique · works with any noun type
the sun · the moon
the door · the sky
the dog I saw
the best day ever
Ø
General concepts · uncountable (general) · plural general
Water is life.
Dogs are friendly.
I love music.
English is fun.

* The tricky cases — see the Sound Trap below.

🔤 A vs AN — It's About Sound, Not Spelling

The rule is simple: use a before a consonant sound and an before a vowel sound. Look at the first sound of the following word — not the first letter.

A
Before a consonant sound: /b/, /k/, /d/, /t/, /j/ (as in "you"), /w/…
a book · a car · a dog
a phone · a house · a table
a university (sounds like "you-niversity" → /j/)
a European city (sounds like "you-ropean" → /j/)
a one-way street (sounds like "wun" → /w/)
AN
Before a vowel sound: /æ/, /e/, /ɪ/, /ɒ/, /ʌ/, /aɪ/…
an apple · an egg
an idea · an umbrella
an hour (H is silent → sounds like "our" /aʊər/)
an honest man (H is silent → /ˈɒnɪst/)
an heir (H is silent → sounds like "air" /eər/)
⚠️ Sound Trap — These Fool Everyone
a hour →
an hour
H is silent → vowel sound /aʊər/
an university →
a university
Starts with /juː/ → consonant Y sound
an European →
a European
Starts with /jʊər/ → consonant Y sound
a honest answer →
an honest answer
H is silent → vowel sound /ˈɒnɪst/
an one-way street →
a one-way street
Starts with /wʌn/ → consonant W sound

🔁 First Mention → A/AN  ·  Second Mention → THE

This is one of the most important patterns in English. The first time you introduce something, the listener doesn't know which one — so you use a / an. The second time, both of you know exactly which one — so you switch to the.

1st mention — New information
I bought a phone yesterday.
The listener has never heard about this phone before. It is brand new information — any phone, one of many.
→
2nd mention — Known information
The phone is very fast.
Now both speaker and listener know exactly which phone we are talking about. We switch to "the".

More Examples of the Pattern

We ate at a restaurant last night. → The restaurant was amazing.
She saw a dog in the park. → The dog was very friendly.
He found a key on the floor. → The key was very old.
There is a cat in my garden. → The cat is sleeping. (↩ connects to Lesson 07!)

📌 THE — More Situations

Besides the "second mention" rule, use the in these situations:

✔ Unique things (only one exists) There is only one → always use the
the sun · the moon · the Earth · the sky · the Internet
✔ Clear from context Both people know exactly which one
Close the door. · Open the window. · Pass the salt.
✔ Superlatives The best, the worst, the most useful… always use the
the best day · the most useful skill · the tallest building
✔ Oceans, rivers & deserts Named geographic features (groups)
the Pacific Ocean · the Amazon River · the Sahara

🚫 Ø — No Article (Speaking in General)

When you talk about a whole category, an abstract concept, or a substance in general — use no article at all.

💧
Uncountable nouns
Water is important.
Music is relaxing.
Homework takes time.
Information is power.
🐶
Plural — in general
Dogs are friendly.
Books are expensive.
Children love to play.
Teachers work hard.
💡
Abstract ideas
Love is powerful.
English is fun.
Freedom matters.
Time flies.

🔊 Listen — Articles in Context

I have a dog.
First mention — any dog
The dog is big.
Second mention — that specific dog
Dogs are friendly.
No article — dogs in general
She is a teacher.
'a' before consonant /t/
He is an engineer.
'an' before vowel /e/
Wait an hour.
'an' — H is silent: /aʊər/
The sun is hot.
'the' — only one sun
I love music.
No article — music in general

❌ Common Mistakes with Articles

She is teacher.
She is a teacher.
In English, professions always need an article — unlike Spanish (ella es profesora).
I have a homework.
I have homework.
"Homework" is uncountable. You cannot say "a homework" — use no article when speaking generally.
Sun is very hot today.
The sun is very hot today.
Unique things — there is only one sun — always take "the".
I like the music. (in general)
I like music.
When talking about music as a concept — not a specific song — drop "the".
I saw a dog. A dog was friendly.
I saw a dog. The dog was friendly.
Second mention → switch from "a" to "the". After the first mention, both people know which dog.
🔗 Connect the Dots — Previous Lessons
L07 There is a cat in the garden. → The cat is sleeping. (first mention = a; second = the)
L08 I have a book. (singular) vs. Books are expensive. (plural general → no article)
2

Prepositions of Time & Place — IN / ON / AT

Tres palabras que ubican todo en el tiempo y en el espacio

Think of prepositions as a zoom lens: IN is the widest shot (big areas, long periods), ON zooms in on specific days and flat surfaces, and AT is the tightest shot — a precise point in time or space.

IN · ON · AT — Full Breakdown

IN Larger areas · Longer periods
⏰ TIME
  • monthsin July
  • yearsin 2020
  • seasonsin winter
  • morning / afternoon / eveningin the morning
📍 PLACE
  • countriesin Mexico
  • citiesin Paris
  • enclosed spacesin the room · in the car
I was born in 2003.
She lives in Costa Rica.
I study in the morning.
ON Specific days · Surfaces
⏰ TIME
  • days of the weekon Monday
  • specific dateson March 15th
  • day + part of dayon Friday morning
📍 PLACE
  • surfaceson the table
  • streetson Main Street
  • floorson the 2nd floor
The meeting is on Tuesday.
The keys are on the table.
She lives on Oak Street.
AT Exact times · Precise points
⏰ TIME
  • exact clock timesat 7:00
  • nightat night
  • holidays (no "day")at Christmas
📍 PLACE
  • specific pointsat the bus stop
  • addresses with numberat 125 Main St.
  • events · work · schoolat the party · at work
Class starts at 9:00 AM.
She is at the airport.
We met at a concert.

📊 Quick Comparison

Preposition TIME — use for PLACE — use for
IN months, years, seasons, morning / afternoon / evening countries, cities, neighborhoods, enclosed spaces
ON days of the week, specific dates, day + part of day surfaces, street names, floors of a building
AT exact clock times, night, holiday periods (at Christmas) specific points, full addresses, events, work, school

📅 A Day at Academia VELA

Every sentence below shows a real situation — and the right preposition to use:

ON
Carlos has English class on Monday.
ON + day of the week
IN
He wakes up in the morning and reviews his notes.
IN + part of the day (morning / afternoon / evening)
AT
His class starts at 9:00 AM.
AT + exact clock time
AT
He studies at Academia VELA.
AT + institution / specific location
IN
The school is in San José.
IN + city
ON
The school is on Maple Street.
ON + street name
ON
Carlos puts his notebook on the desk.
ON + surface
IN
He drives to class. He listens to English podcasts in the car.
IN + enclosed space
AT
After class, he has coffee at a café on Oak Street.
AT + specific place · ON + street name
IN
Carlos started learning English in 2024 — one of the best decisions of his life.
IN + year

🔊 Listen — Prepositions in Context

I study in the morning.
in + part of day
The meeting is on Monday.
on + day of the week
Class starts at 9:00 AM.
at + exact time
She lives in Costa Rica.
in + country
The keys are on the table.
on + surface
She is at the airport.
at + specific location
He is in the car.
in + enclosed space
We go to church on Sunday.
on + day of the week

❌ Common Mistakes with Prepositions

I live at Mexico.
I live in Mexico.
Countries use IN — they are large areas, not specific points. AT is too precise for a country.
The book is in the table.
The book is on the table.
A table is a surface → ON. "In the table" would mean the book is inside the wood itself.
See you in Friday.
See you on Friday.
Days of the week always use ON — no exceptions.
The bus arrives in 3:00.
The bus arrives at 3:00.
Exact clock times always use AT. IN is for longer periods (months, years, seasons).
He is at the car right now.
He is in the car right now.
A car is an enclosed space → IN. "At the car" means standing next to it outside.

📖 Reading: "Carlos's English Journey"

Read the passage carefully. Articles and prepositions are color-coded:

Carlos's English Journey
A short story about a student at Academia VELA · Articles & Prepositions highlighted
A AN THE IN ON AT

Carlos is a student at Academia VELA. He lives in a small apartment on Maple Street, in the city of San José. Every Monday morning, he wakes up at 7:00 AM, makes an espresso, and gets in the car to drive to class.

His English class starts at 9:00 AM on Mondays. Carlos always puts a book and a notebook on his desk. The book is about grammar, and the notebook is full of vocabulary words.

His teacher is an honest and patient woman named Sofia. She is a very experienced teacher. The teacher always begins with a warm greeting and an interesting question for the class.

In the afternoon, after class, Carlos walks to a coffee shop on Oak Street. He orders an orange juice and opens his grammar book. He thinks to himself: "I love the examples in this book — they are so clear and useful!"

In the evening, Carlos reviews his notes at home. He was born in 2003, and he started studying English in 2024. He wants to be an engineer someday. He knows that English is the most useful skill he can learn right now — and starting was, without a doubt, one of the best decisions of his life.

✏️ Reading Comprehension Quiz

8 questions about the passage above:

🎯 Practice Quiz — Articles & Prepositions

20 questions — 10 on articles and 10 on prepositions. Take your time!