Idiomatic Prepositions

Idiomatic prepositions are specific prepositions that always go with certain adjectives or verbs. Unlike regular prepositions that describe place or time, these combinations must be memorised because they follow no logical rule -- they are simply how English works.

What You'll Learn

At the P5 level, you will learn:

• Common adjective + preposition combinations such as afraid of, good at, interested in, and keen on
• How to choose the correct preposition for frequently tested expressions
• How to avoid mixing up prepositions in fixed combinations
• How to use these expressions naturally in your own sentences

When to Use

1. Describing feelings about something: "She is afraid of the dark."
2. Talking about someone's abilities: "My brother is good at Mathematics."
3. Expressing curiosity or enthusiasm: "We are interested in learning about volcanoes."
4. Showing eagerness or desire: "The students are keen on joining the science club."
5. Writing compositions or answering cloze passages: "He was proud of his achievement in the spelling bee."

How to Form

Adjective + Preposition Combinations

Each adjective is paired with a fixed preposition. The pattern is:

Subject + be + adjective + preposition + noun/gerund

Using a Gerund (-ing) After the Preposition

When a verb follows the preposition, it must be in the -ing form (gerund):

Key Rules

1. Each adjective has a fixed preposition: You must memorise which preposition goes with which adjective. There is no shortcut -- "afraid" always takes "of", never "about" or "at".

2. Do not swap prepositions: "Good at" is correct, but "good in" is wrong. Even though both "at" and "in" are common prepositions, only "at" is correct with "good" when describing ability.

3. Use the -ing form after the preposition: When a verb follows the preposition, always change it to the gerund. Say "keen on reading", not "keen on read".

4. The preposition stays the same regardless of tense: Whether the sentence is in past, present, or future tense, the preposition does not change. "She was afraid of dogs" and "She is afraid of dogs" both use "of".

5. Do not confuse "interested in" with "interested to": In standard English, "interested in" is used with nouns and gerunds. "I am interested in joining" is correct, not "I am interested to join".

6. "Good at" vs "good for": These have different meanings. "Good at" means skilful ("She is good at cooking"), while "good for" means beneficial ("Exercise is good for your health").

Common Mistakes

Clue Words

Preposition "of"

afraid, fond, proud, tired, scared, aware

Preposition "at"

good, bad, terrible, excellent, skilled

Preposition "in"

interested, involved, engaged

Preposition "on"

keen, dependent, intent

Preposition "about"

worried, excited, curious, serious, concerned

Tip: Group the adjectives by their preposition and memorise them in "families". Think of "of" as the "feelings family" (afraid of, fond of, proud of) and "at" as the "skills family" (good at, bad at, excellent at). This makes them much easier to remember.

Practice Tips

1. Flashcard pairs: Write the adjective on one side and the preposition on the other. Test yourself daily until the combinations feel automatic.
2. Sentence building: Pick one adjective-preposition pair each day and write three sentences using it -- one about school, one about home, and one about a hobby.
3. Elimination strategy for exams: In a cloze passage or MCQ, read the adjective and immediately recall its fixed preposition. If you see "afraid", the answer must be "of" -- no need to consider other options.
4. Read and highlight: When reading storybooks or news articles, underline any adjective + preposition combinations you spot. This builds familiarity with how they appear in real sentences.

Quick Reference