'Interested In' or 'Interested On': What's the Correct Preposition to Use?

Prepositions are a tricky part of the English language. Knowing which ones to use and when doesn’t always make sense. For instance, should you say ‘interested in’ or ‘interested on’? 

In this article, we’re going to learn about the different types of prepositions, their meaning, and when they can be used, as well as a very important concept that will really help you with this particular case: preposition collocations. 

If you're just looking for the hard and fast answer to your question, the correct preposition to use in this context is 'in'.

Indeed, you should always say 'interested in' and never 'interested on'.

What Does It Mean? 

So what does this phrase mean? And how can you use it in a sentence? That is what we are about to find out. Read on.

What Does ‘Interested’ Mean? 

‘Interested’ is a past-participle adjective that stems from the verb ‘interest’. It means to have your attention engaged, and has its roots in the 16th-century word ‘interesse’. 

Tell me more - I’m interested.

The word ‘interested’ can also be used to refer to a group of people concerned about a particular matter. For example:

Would all interested parties please get in touch with the Department of Corrections.

But this meaning is beyond the scope of this article, so for today, we’ll focus on the first meaning - that of having an interest in a topic or person. 

What Does ‘In’ Mean

‘In’ is a preposition used to indicate where a person or thing is in time or space. 

• She’s in her room.
• That was back in 1956.
• Teotihuacan is in Mexico.

The word ‘in’ carries several other meanings, which we encourage you to research if you’re interested (see what we did there?). But for the purposes of this article, we only need this particular meaning.

“Are You Interested In” Meaning

Between ‘interested in’ and ‘interested on’, the correct way is ‘interested in’. 

To be interested in something means that you’d like to know more about it. It’s used to refer to something you like to spend time focusing on. 

I used to hate geography at school but now I’m really interested in it.

Interestingly (ooh, we did it again!), using it to refer to a person usually implies some kind of romantic interest.  Here are some examples:

• Polly’s clearly interested in you - she keeps staring. 
• Dan said Polly’s into me, but I’m not interested.

How Do You Use “Interested in” in a Sentence?

In order to build a sentence, here’s the structure to follow:

Subject + ‘interested in’ + object.

For example:

My sister is interested in geography.

You could also extend this sentence by adding some more information:

My sister is interested in geography, even though she used to hate it at school. 

Another common way to use it is to combine it with a gerund. As a reminder, a gerund is a word that looks like a verb in the present continuous form but is used as a noun. For example:

• I’m really interested in learning the piano.
• Would you be interested in going for lunch this weekend?

Understanding Prepositions

Prepositions can be a little tricky to wrap your head around. Let's review the basics.

What Are Prepositions?

Let’s chat a little bit more about prepositions. We feel it’s important to understand them if you’re going to use them properly. So let’s start with the different types of prepositions. Here are the main types, with some examples:

• Prepositions of place (in, on, out)
• Prepositions of time (before, after)
• Prepositions of direction (to, from)

In a sentence, prepositions come before a noun or pronoun, or a noun phrase. In the following example, ‘in’ is the preposition and ‘bed’ is the noun.

Leave me alone, I’m still in bed. 

To list another example, here the preposition is ‘behind’ and the pronoun is her.

I’m standing behind her in the queue. 

The Preposition ‘In’

The preposition ‘in’ falls under the category of preposition of place, but also time. Indeed, you could use it to refer to where something is, but also when it was. For example:

• The dog’s in his bed.
• That movie was made in 2001.

A fun addition to the categories of prepositions that we didn’t mention, and that ‘in’ belongs to, is metaphorical prepositions. For example, you might say that you’re ‘in love’ or ‘in danger’. You aren’t literally in those things, but it’s a metaphorical container.

Colloquially, ‘in’ can also be used to refer to something that’s fashionable.

Trench coats are so in this season.

Or even to refer to a group of people who are also, in a way, trendy and fashionable. 

She’s in with the 'in' crowd.

Prepositional Phrases

As we’ve mentioned already, the correct way to express interest is always to say ‘interested in’. 

But why? If, as we just learned, ‘in’ is a preposition of place or location, then surely it doesn’t make any sense to combine it with ‘interested’? After all, an interest isn’t a location. 

This is where prepositional phrases come in. Also sometimes referred to as 'prepositional collocations’, prepositional phrases refer to an inseparable combination of a noun, verb, or adjective with a preposition. There is no logic to these combinations, they just exist together and can’t be separated. That’s just the way it is, and there’s no rule to help you remember how they fit together. Your only way is to remember them by heart.

Sorry!

Some common prepositional phrases include:

• Suffer from
• On foot
• Account for
• Content with
• Addicted to
• Persist in

And of course, ‘interested in’.

That’s the reason why ‘interested in’ is correct, and ‘interested on’ isn’t. Because ‘interested’ and ‘in’ are bound together by the magic of prepositional phrases.

Different Combinations of 'Interested' and Prepositions

There are different ways that 'interested' can be combined with prepositions. We will explain it below.

Interested In vs. Interested To

While we’ve now determined that you can’t say ‘interested on’ if you want to express an interest in something, you might have heard or seen the expression ‘interested to’. What does this mean, and how do you use it?

‘Interested to’ must always be followed by a perception verb, and the verb must be in the infinitive form (i.e. not conjugated). Perception verbs are actions that involve your five senses, or in other words, that convey the experience of the physical senses.  Here are a few examples:

• Hear
• Listen 
• See
• Look
• Notice
• Smell 
• Know 
• Find out 

So for example, you might say:

I’m interested to hear what she has to say for herself.

Can You Ever Use ‘Interested On’?

So we know we said that you couldn’t use ‘interested on’, but you might see it around, so we wanted to clarify situations where you could use it or similar expressions. Let us explain what we mean.

You could use ‘interested on’ to say that you were interested in something on a particular day. For example:

The lottery? Oh yeah, I was interested on Monday when I heard about it but I’ve changed my mind. 

You could use ‘interest on” in the context of finances.

What’s the interest on late payments?

It's important to note, though, that this is different from ‘interested on’, as ‘interest’ here is a noun, and not an adjective. 

We hope this has been helpful for you in understanding why you can use one phrase but not the other when it comes to expressing your interest. 

In summary, the correct way is always ‘interested in’ and never ‘interested on’, and the reason for this is, quite simply, because it’s a prepositional phrase, which means those two words are inseparable in that context.

In any case, we hope that you were interested in reading this article!