Articles (a, an, the) and prepositions (in, on, at, of, by) cause the most small errors in English. This note teaches the rules through patterns, not memorization.
Imagine telling someone "I saw movie in theater." Something sounds wrong immediately. The correct sentence is "I saw a movie at the theater."
Articles (a, an, the) and prepositions (in, on, at, with, by, of, for, to) are tiny words that carry enormous weight in English. Getting them wrong signals poor command of the language. Getting them right signals mastery.
For CAT, these errors appear in Fill in the Blanks, Sentence Correction, and RC comprehension questions.
Articles and preposition errors are among the most commonly tested in CAT English. These are also the errors most non-native English speakers make — making them ideal for differentiating between test-takers.
English has three articles:
| Article | When to Use | Example |
|---|---|---|
| A | First mention; one of many; consonant sound | a book, a university (not a vowel sound!) |
| An | First mention; one of many; vowel sound | an apple, an hour (silent 'h') |
| The | Specific; unique; previously mentioned; superlatives | the book (we discussed), the sun, the best |
| (None) | Plural/uncountable in general; proper nouns | Books are useful. Honesty matters. India is big. |
Vowel sound rule: "an" before the SOUND, not the letter.
Rule 1: When the noun is already known (mentioned before or contextually obvious).
"I bought a car. The car is red." (Second mention → the)
Rule 2: Unique things (only one exists).
"The sun, the moon, the Earth."
Rule 3: Superlatives.
"She is the best student."
Rule 4: Ordinal numbers.
"The first chapter."
Rule 5: Specific geographical features.
Rule 6: Musical instruments.
"She plays the piano." ✓
Rule 7: Names of newspapers.
"The Hindu, The Times of India."
| Preposition | Use | Examples |
|---|---|---|
| AT | Specific time; festivals | at 5pm, at noon, at midnight, at Diwali |
| ON | Days; dates | on Monday, on 15 August, on my birthday |
| IN | Months; years; seasons; longer periods | in January, in 2024, in summer, in the morning |
| FOR | Duration | for 3 hours, for two years |
| SINCE | Starting point | since 2010, since Monday |
| BY | Deadline | by Friday, by noon |
| DURING | Throughout a period | during the meeting, during vacation |
| WITHIN | Before the end of a period | within 5 days |
Memory trick for AT/ON/IN:
| Preposition | Use | Examples |
|---|---|---|
| AT | Specific location/point | at the station, at home, at school |
| IN | Inside/enclosed space; cities/countries | in the room, in India, in a box |
| ON | Surface; floor level | on the table, on the wall, on the 3rd floor |
| BY / BESIDE | Next to | by the river, beside the road |
| BETWEEN | Two items | between A and B |
| AMONG | Three or more | among the students |
| ABOVE / BELOW | Vertical position (not touching) | above the clouds, below sea level |
| OVER / UNDER | Directly above/below; sometimes covering | over the bridge, under the table |
Many verbs, adjectives, and nouns take fixed prepositions. These must be memorized:
Verb + Preposition:
| Expression | Correct Preposition |
|---|---|
| Agree WITH someone | agree with her |
| Agree ON something | agree on the plan |
| Differ FROM | different from (NOT different to or than) |
| Depend ON | depend on circumstances |
| Consist OF | consists of three parts |
| Result IN | resulted in failure |
| Result FROM | resulted from negligence |
| Responsible FOR | responsible for the outcome |
| Interested IN | interested in history |
| Good AT | good at math |
| Married TO | married to him |
| Proud OF | proud of her work |
| Apologize FOR | apologize for the delay |
| Divide INTO | divided into three parts |
Common errors:
✗ "She is different than her sister." → ✓ "different from"
✗ "She is married with him." → ✓ "married to"
✗ "He is good in math." → ✓ "good at math"
✗ "This consists from three parts." → ✓ "consists of"
| Preposition | Use | Example |
|---|---|---|
| TO | Destination | Go to school |
| INTO | Movement inside | Walk into the room |
| ONTO | Movement on top | Jump onto the table |
| FROM | Origin | Come from Mumbai |
| THROUGH | Pass within something | Drive through the tunnel |
| ACROSS | Pass over a surface | Walk across the bridge |
| ALONG | Follow a path | Walk along the road |
| PAST | Go beyond | Drive past the signal |
"In" vs "At" for institutions:
✗ "She studied at the university campus in the library."
→ Attend (university as institution) = AT; physical location inside = IN
✓ "She studied at the university." (institution) "She was in the library." (location)
"Between" vs "Among":
✗ "Distribute these among the two friends." → "between" (2 people)
✗ "This is a secret between the three of us." → "among" (3+ people)
✓ Between = exactly 2. Among = 3 or more.
"In" vs "Within":
"Submit by Friday" = deadline.
"Submit within 3 days" = duration from now.
| Term | Meaning |
|---|---|
| Article | A word (a/an/the) placed before a noun |
| Definite Article | "The" — refers to a specific noun |
| Indefinite Article | "A/An" — refers to any one of a class |
| Preposition | Word showing relationship (time, place, direction) |
| Collocation | Fixed combination (e.g., "good at," "responsible for") |
| Zero Article | No article used (general plural/uncountable nouns) |
Fill in the blank with a/an/the or nothing (—):
Choose the correct preposition:
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