Good At, Interested In: The Prepositions You Cannot Guess
Interested on music. Depends of you. Good in maths. These are not careless errors and they are not random either. Each one is a word that takes a fixed preposition in English, chosen by usage rather than by logic, and the learner has picked the preposition their own language would use.
English attaches a fixed preposition to a large number of verbs, adjectives and nouns. Depend takes on. Interested takes in. Reason takes for. The preposition carries almost no meaning of its own, which is precisely the problem: there is nothing in the meaning to reason from, so the pairing has to be known rather than worked out.
This is why the errors are so persistent. A learner who says interested on music has not misunderstood anything about English. They have applied the preposition their first language uses, which is the only available strategy when no rule exists.
Three places they appear
Fixed prepositions follow verbs, adjectives and nouns, and the three groups behave slightly differently in how often they are noticed. Verb pairs get corrected early because they appear constantly. Noun pairs survive much longer, because they mostly appear in writing.
| After a | Common pairs | Where errors show up |
|---|---|---|
| Verb | depend on, listen to, wait for, apologise for, belong to, rely on | Speech, constantly, so they get corrected early |
| Adjective | good at, interested in, afraid of, proud of, worried about, similar to | Speech and writing equally |
| Noun | reason for, need for, increase in, solution to, interest in | Formal writing, where they often survive uncorrected to C1 |
The verb form that follows
Once the preposition is right, a second error waits behind it. A verb after a preposition takes the -ing form, not the infinitive. Interested in learning, not interested in learn. Good at cooking. Apologise for being late.
This catches even advanced learners in one specific place: I am looking forward to meeting you. The to here is a preposition rather than part of an infinitive, so meeting is correct and meet is not. The phrase appears in almost every formal email, which is what makes the error so visible.
When the preposition changes the meaning
Most fixed pairs are simply fixed. A smaller group takes more than one preposition, and the choice changes what the sentence says. These are worth learning as contrasts rather than as separate entries, because meeting one without the other is what produces confident mistakes.
- good at is about skill; good for is about benefit. She is good at running, and running is good for you.
- sorry about expresses regret for a situation; sorry for expresses pity for a person.
- worried about is the ordinary version; worried by points at a specific cause.
- similar to compares two things; similar in names the respect in which they are alike.
Why these are not phrasal verbs
Wait for and give up look like the same structure, and treating them the same way is a common cause of confusion. In wait for, the preposition is a fixed partner that leaves the meaning alone: waiting for something is still waiting. In give up, the particle creates a meaning the verb does not have, which is what makes it a phrasal verb.
The practical consequence is that they need different storage. A phrasal verb needs its whole meaning recorded, because the meaning is the unpredictable part. A fixed preposition needs only the pair, because the meaning was never in doubt. The phrasal verb side is covered in phrasal verbs at B2.
How to learn something with no rule behind it
Grammar that has a rule can be understood once and applied afterwards. This has no rule, so understanding gives you nothing and only exposure and retrieval do. That changes the method rather than the effort.
The single most useful habit is to stop recording the word alone. A vocabulary note that says interested is almost worthless, because the difficult part was never the meaning. A note that says interested in something carries the part that will actually be wrong later.
This is the same principle that makes chunks beat single words generally, described in collocations, chunks and phrasal verbs. Fixed prepositions are simply the clearest case of it, because there is no meaning to fall back on when the chunk is not there.
| Recorded as | What happens later |
|---|---|
| depend | The meaning is known and the preposition is guessed, usually from the first language |
| depend on someone | The pair is retrieved as one unit, and the error never gets the chance to form |
| It depends on the weather | The pair arrives with a situation, which makes it far easier to produce under pressure |
Why exams test them so heavily
Cambridge and other exam papers use open cloze tasks where a single word has to be supplied with no options given, and fixed prepositions are ideal material for them. They cannot be guessed from context, they cannot be reasoned out, and they distinguish a learner who has read widely from one who has studied rules.
That makes them unusually good value for exam preparation, because the set is finite and the marks are real. What to prioritise for the Cambridge exams specifically is covered in what B2 First actually tests and what C1 Advanced tests.
The twenty worth securing first
If the whole area feels shapeless, start with the pairs that appear in ordinary conversation every day. Secure these, then let reading supply the rest.
- depend on, rely on, insist on, concentrate on
- listen to, belong to, happen to, look forward to
- wait for, apologise for, pay for, blame someone for
- good at, bad at, interested in, afraid of, proud of, worried about, similar to, responsible for