What Are Prepositions? Grammar Guide + Examples

By the time you’re reading this, you must have now realized that English grammar has more rules and laws than the US Constitution.

You’ve got subject-verb agreement, verb tenses, and the most confusing one of all: prepositions.

Prepositions are like your exes.

The moment you forget how they relate to the subject, it gets awkward fast. That’s why there are rules to prevent these misunderstandings, like saying “in the car” but “on the bus” or “on the phone” but “in a meeting” to clarify. 

With the right understanding of what they do, when to use them, and how to avoid common mistakes, understanding prepositions will be a piece of cake. 

Let’s get into it. 

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Key Takeaways

• Prepositions show relationships between words in sentences, typically indicating time, place, or direction.

• There are three main types: simple, compound, and phrasal prepositions that serve different functions.

• Most prepositions come before nouns or pronouns to form prepositional phrases that add detail to sentences.

• Common mistakes include confusing prepositions with conjunctions or adverbs, and mixing up similar prepositions.

• Practice and pattern recognition are essential for mastering preposition usage in everyday writing.

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What Is a Preposition?

Prepositions are like relationship counselors for words.

They don’t do much on their own, but they’re fantastic at explaining how different parts of your sentence connect.

A preposition is a word that shows the relationship between a noun (or pronoun) and other words in a sentence.

These relationships usually involve location, time, direction, or manner. Without prepositions, our sentences would sound like a toddler’s first attempts at storytelling.

Consider these examples:

• “The cat sat the table” (What? Where exactly?)
• “The cat sat on the table” (Ah, now we get it!)

The preposition “on” tells us exactly where that cat decided to park itself.

It creates a bridge between “sat” and “table,” giving us the full picture.

Most prepositions are short words. 

We’re talking about everyday words like in, on, at, by, for, with, about, through, and during. But don’t let their size fool you.

These little words pack a serious punch when it comes to meaning.

Some prepositions can wear multiple hats too. The word “before” can be a preposition (“before dinner”) or a conjunction (“before I leave”). 

Context is everything.

If you’re ever unsure whether a word functions as a preposition, try this simple test:

Can you put a noun or pronoun right after it to make sense? If yes, you’ve probably got yourself a preposition.

Alternatively, you can use Undetectable AI’s Ask AI, which can help clarify if a word in your sentence is functioning as a preposition or something else entirely.

It’s like having a grammar expert in your back pocket.

Types of Prepositions

Not all prepositions fall into the same category.

They come in three main flavors, each with its own personality and purpose.

Simple Prepositions

These are your basic, no-frills prepositions. Single words that get straight to the point.

Think of them as the jeans and t-shirt of the grammar world: reliable, versatile, and always appropriate.

Common simple prepositions include: at, in, on, by, for, with, about, under, over, through, during, before, after, between, among, above, below, beside, behind, and against.

Examples:

• “I’ll meet you at the coffee shop.”
• “She walked through the park.”
• “The book is under the couch.”

Compound Prepositions

These are two or more simple words that team up to function as a single preposition. They’re like word partnerships that decided to make it official.

Popular compound prepositions include: into, onto, upon, within, without, throughout, underneath, alongside, and outside.

Examples:

• “He jumped into the pool.”
• “The keys fell underneath the car.”
• “We traveled throughout Europe.”

Phrasal Prepositions

These are groups of words that work together as a prepositional unit.

They’re more complex but often more specific in their meaning. Think of them as the specialized tools in your grammar toolbox.

Common phrasal prepositions include: in front of, in spite of, on behalf of, with regard to, in addition to, due to, according to, and instead of.

Examples:

• “She stood in front of the mirror.”
• “According to the weather report, it’ll rain.”
• “In spite of the traffic, we arrived on time.”

Each type serves its purpose. Simple prepositions handle everyday relationships.

Compound prepositions often show movement or change. Phrasal prepositions get specific about complex relationships that single words can’t quite capture.

How to Use Prepositions in Sentences

Now that you know what prepositions are, let’s talk about putting them to work.

Position Before Nouns or Pronouns

This is the golden rule of preposition placement.

Prepositions almost always come directly before their object (the noun or pronoun they relate to other parts of the sentence).

The basic pattern looks like this: Preposition + Object = Prepositional phrase

Examples:

• In the morning (in + morning)
• With her (with + her)
• During class (during + class)
• Behind the building (behind + building)

Sometimes you’ll see multiple prepositions working together, but each one still needs its object:

• “The cat ran from under the table to behind the couch.”

Prepositional Phrases

When a preposition teams up with its object, they form what we call a prepositional phrase.

These phrases work as units to modify other words in your sentence.

Prepositional phrases can act like adjectives (describing nouns) or adverbs (describing verbs, adjectives, or other adverbs).

Acting like adjectives:

• “The house on the hill is beautiful.” (Which house? The one on the hill.)
• “Students in my class are hardworking.” (Which students? The ones in my class.)

Acting like adverbs:

• “She arrived at midnight.” (When did she arrive? At midnight.)
• “He spoke with confidence.” (How did he speak? With confidence.)

Subject-Verb Agreement with Prepositional Phrases

Here’s where things get tricky. Prepositional phrases can sneak between subjects and verbs, trying to confuse you about which noun the verb should agree with.

The key rule: The verb agrees with the subject, not with the object of the preposition.

Correct: “The box of cookies is on the table.” 

Incorrect: “The box of cookies are on the table.”

Why? Because “box” is the subject (singular), not “cookies” (which is just the object of the preposition “of”).

Another example: 

Correct: “One of the students has finished the assignment.”

Incorrect: “One of the students have finished the assignment.”

The subject is “one” (singular), not “students” (plural).

Undetectable AI’s Grammar Checker can flag incorrect prepositional phrases and placement in your writing, helping you catch these tricky agreement issues before they become problems.

Prepositions in Questions and Negatives

Questions and negative statements can make preposition usage feel like you’re trying to solve a puzzle blindfolded.

But there are patterns here too.

Questions with Prepositions

In formal writing, prepositions often stay with their objects even in questions:

• “To whom did you give the book?” (formal)
• “With what did she write the letter?” (formal)

In casual conversation, we usually move the preposition to the end:

• “Who did you give the book to?” (casual)
• “What did she write the letter with?” (casual)

Both are correct, but know your audience. Academic papers prefer the formal structure. Text messages to your friends? Go casual.

Wh- questions often need prepositions to make complete sense:

• “Where are you going to?”
• “What are you thinking about?”
• “Who are you talking with?”

Negative Statements

Prepositions in negative sentences work the same way as in positive ones. The “not” doesn’t change the preposition’s relationship to its object.

Examples:

• “She is not in the office.”
• “We did not go to the party.”
• “He cannot work without his coffee.”

Sometimes the negative can create interesting meaning changes:

• “I agree with you.” vs. “I do not agree with you.”
• “She walked into the room.” vs. “She did not walk into the room.”

The preposition stays the same, but the entire meaning flips.

Common Mistakes and How to Fix Them

Let’s be real. Everyone messes up prepositions. Even native speakers get them wrong sometimes.

Here are the mistakes that pop up most often and how to avoid them.

1. Mixing Up Similar Prepositions

The classic confusion trio: in, on, and at.

For time:

• In = months, years, seasons (“in January,” “in 2023,” “in winter”)
• On = days, dates (“on Monday,” “on March 15th”)
• At = specific times (“at 3 p.m.,” “at noon,” “at midnight”)

For place:

• In = enclosed spaces (“in the house,” “in the car,” “in the box”)
• On = surfaces (“on the table,” “on the wall,” “on the bus”)
• At = specific locations or points (“at the store,” “at home,” “at the corner”)

Wrong: “I’ll see you on 5 p.m. in Monday.” Right: “I’ll see you at 5 p.m. on Monday.”

2. Ending Sentences with Prepositions

Your English teacher probably told you never to end sentences with prepositions. That rule is more like a guideline now, especially in casual writing.

Overly formal: “About what are you thinking?” 

Natural: “What are you thinking about?”

Sometimes, avoiding the final preposition creates awkward sentences. When in doubt, choose clarity over rigid rules.

3. Using the Wrong Preposition with Specific Words

Some words have preferred preposition partners. These combinations are called collocations, and they mostly come down to memorization.

Common collocations:

• Interested in (not “interested about”)
• Good at (not “good in” for skills)
• Afraid of (not “afraid from”)
• Married to (not “married with”)
• Different from (not “different than” in formal writing)

4. Redundant Prepositions

Sometimes we add prepositions where they don’t belong:

Wrong: “Where are you going to?” Right: “Where are you going?”

Wrong: “I can’t remember where I put it at.” Right: “I can’t remember where I put it.”

The “where” already includes the idea of location, so the extra preposition is unnecessary.

5. Missing Prepositions

On the flip side, sometimes we forget prepositions entirely:

Wrong: “She arrived the party late.” Right: “She arrived at the party late.”

Wrong: “We talked the problem.” Right: “We talked about the problem.”

Prepositions vs Other Word Classes

This is where prepositions like to play dress-up and pretend to be other parts of speech.

Prepositions vs Conjunctions

Same word, different job. The difference is what comes after them.

Preposition + noun/pronoun:

• “Before the movie, we got popcorn.” (Before + noun)
• “She left after him.” (After + pronoun)

Conjunction + clause (subject + verb):

• “Before we watched the movie, we got popcorn.” (Before + clause)
• “She left after he arrived.” (After + clause)

The word stays the same, but its function changes based on what follows.

Prepositions vs Adverbs

Some words can be prepositions or adverbs depending on whether they have an object.

Preposition (has an object):

• “She walked up the stairs.” (up + stairs)
• “The cat jumped over the fence.” (over + fence)

Adverb (no object):

• “She walked up.” (just up, no object)
• “The cat jumped over.” (just over, no object)

Transitional Phrases That Look Like Prepositions

Phrases like “in addition,” “for example,” and “on the other hand” might look like prepositional phrases, but they’re actually transitional expressions that connect ideas.

Transitional phrase: “In addition, we need to consider the cost.” 

Prepositional phrase: “In addition to the cost, we need to consider time.”

The first connects two independent ideas. The second shows a relationship between “addition” and “cost.”

Undetectable AI’s AI Humanizer can help refine your word choice when prepositions are misused or sound ambiguous, making your writing clearer and more natural.

Practice Activities

Theory is great, but prepositions need practice. Like learning to drive or mastering a video game, you need repetition to build muscle memory.

Fill-in-the-Blank Exercises

Start with sentences that have missing prepositions. Try to fill them in based on context:

1. “I’ll meet you ___ the library ___ 3 p.m.”
2. “The keys are ___ the drawer ___ the kitchen.”
3. “She’s been working ___ this project ___ two weeks.”

(Answers: 1. at, at; 2. in, in; 3. on, for)

Sentence Correction

Find the preposition errors in these sentences:

1. “I’m interested about learning Spanish.”
2. “Where did you put the book at?”
3. “She arrived to the party early.”

(Corrections: 1. interested in; 2. remove “at”; 3. arrived at)

Writing Practice

Write short paragraphs using specific prepositions. Challenge yourself to use each preposition correctly:

Write about your morning routine using: in, at, on, during, after, before 

Write about the room you’re in using: under, over, beside, behind, in front of, between

Reading Analysis

Take a paragraph from any book or article. Circle all the prepositions. Identify what type each one is (simple, compound, or phrasal). Notice how they connect ideas and add detail to the writing.

Conversation Practice

In your daily conversations, pay attention to prepositions. When you catch yourself using one incorrectly, stop and correct yourself. This builds awareness and helps train your ear for what sounds right.

To make things more fun, Undetectable AI’s AI Chat offers interactive grammar practice and sentence correction games that make learning prepositions more engaging than traditional exercises.

Start optimizing your content—use our AI Detector and Humanizer below.

It’s Never Just the Subject

Prepositions might be small, but they can shape the meaning of an entire sentence.

They determine direction, clarify meaning, and turn clunky sentences into clean, confident writing.

Don’t stress over perfection. Even native speakers second-guess in, on, and at. What matters is understanding the patterns and practicing in context.

And when you’re stuck?

Undetectable AI has tools to clean up those confusing phrases and tighten your writing fast, without sounding robotic.