Have you ever wondered why we say “after dinner” in one sentence but “after dinner ended” in another? Both expressions are correct, yet traditional English grammar classifies the word after differently in each one.
In “after dinner,” the word after is a preposition because it introduces a noun phrase. In “after dinner ended,” it is traditionally called a subordinating conjunction because it introduces a clause.
Understanding preposition vs. conjunction helps you build better sentences, connect ideas naturally, and avoid common grammar mistakes.
Prepositions and conjunctions are both important parts of English grammar, but they serve different purposes. Prepositions typically introduce phrases that express relationships involving time, place, direction, cause, and other meanings. Conjunctions connect words, phrases, or clauses.
Some words, including before, after, since, and until, can appear in both types of structures. Their classification also depends on the grammar framework being used.
This guide explains the difference between prepositions and conjunctions with easy rules, comparison charts, 40 numbered examples, practical writing tips, common mistakes, six practice questions, and eight FAQs.
Quick Answer: Preposition vs. Conjunction
A preposition typically introduces a phrase that shows a relationship between people, things, events, or ideas. A conjunction connects grammatical units or introduces a dependent clause.
Compare:
- “The keys are under the table.” — Under is a preposition.
- “I bought tea and coffee.” — And is a coordinating conjunction.
- “I stayed home because I was sick.” — Because is a subordinating conjunction.
- “We left after lunch.” — After is traditionally a preposition.
- “We left after lunch ended.” — After is traditionally a subordinating conjunction.
Easy memory trick: A preposition expresses a relationship; a conjunction connects grammatical units.
TL;DR: Preposition vs. Conjunction
- Prepositions commonly introduce phrases showing time, place, direction, cause, or other relationships.
- Conjunctions connect words, phrases, or clauses.
- Common prepositions include in, on, at, under, beside, between, and during.
- Common conjunctions include and, but, or, because, although, if, and unless.
- In traditional grammar, before, after, since, and until can be prepositions or subordinating conjunctions.
- Some modern grammars classify these words as prepositions in both uses.
| Feature | Preposition | Conjunction |
|---|---|---|
| Main function | Expresses a relationship | Connects grammatical units |
| Common examples | In, on, under, beside | And, but, because, although |
| Typical structure | Preposition + noun phrase | Conjunction + word, phrase, or clause |
| Example | After lunch | After lunch ended |
| Shows time? | Yes | Yes |
| Shows cause? | Yes | Yes |
Preposition vs. Conjunction: Quick Difference
The easiest way to understand preposition vs. conjunction is to examine how the word works in a sentence.
In traditional school grammar, a preposition commonly comes before a noun, pronoun, or noun phrase.
For example:
“She waited until midnight.”
Here, until introduces the noun midnight.
A subordinating conjunction introduces a dependent clause.
“She waited until the clock struck midnight.”
Here, until introduces the clause the clock struck midnight.
Side-by-Side Examples
| Preposition use | Conjunction use |
|---|---|
| Before dinner | Before dinner started |
| After school | After school ended |
| Since Monday | Since the meeting began |
| Until midnight | Until the clock struck midnight |
These classifications follow traditional school grammar. Some modern grammars classify words such as before and after as prepositions even when they introduce clauses.
A Simple Three-Step Identification Method
Step 1: Find the word you want to identify.
Step 2: Look at the grammatical structure it introduces or connects.
Step 3: Ask whether it introduces a relational phrase, connects equal units, or introduces a dependent clause.
For example:
“She studied in the library because she had an exam.”
Here:
- In introduces the noun phrase the library.
- Because introduces the dependent clause she had an exam.
Key takeaway: The word’s grammatical function matters more than memorizing a list.
What Is a Preposition?
A preposition is a word that typically introduces a phrase and expresses a relationship between its complement and another part of the sentence.
Prepositions can describe place, time, direction, movement, cause, purpose, means, and other relationships.
Prepositions of Place
These describe where something is located.
Examples:
- The cat is under the chair.
- The keys are on the table.
- She stood beside her friend.
Prepositions of Time
These describe when something happens.
Examples:
- The meeting begins at noon.
- We arrived before dinner.
- She has worked here since 2020.
Prepositions of Direction
These describe movement or direction.
Examples:
- He walked into the room.
- They traveled toward the city.
- She ran across the field.
Prepositions of Cause and Purpose
Some prepositions explain reasons or purposes.
Examples:
- The game was canceled because of rain.
- She studied for the exam.
- He succeeded through hard work.
Common Prepositions Chart
| Preposition | Example | Relationship |
|---|---|---|
| In | In the box | Place |
| On | On the table | Place |
| At | At noon | Time |
| Under | Under the bed | Place |
| Between | Between two buildings | Position |
| Before | Before dinner | Time |
| After | After lunch | Time |
| Into | Into the room | Direction |
| During | During class | Time |
| Because of | Because of traffic | Cause |
Important: A preposition does not always describe physical location. It may express time, reason, manner, comparison, or another relationship.
What Is a Conjunction?
A conjunction connects words, phrases, or clauses.
Conjunctions help writers combine related information and show how ideas are connected.
Traditional English grammar recognizes three major types: coordinating, subordinating, and correlative conjunctions.
Coordinating Conjunctions
Coordinating conjunctions connect grammatical units of equal status.
The familiar FANBOYS list includes:
- For — reason
- And — addition
- Nor — negative alternative
- But — contrast
- Or — choice
- Yet — contrast
- So — result
Examples:
“I bought apples and oranges.”
“She was tired, but she continued working.”
Subordinating Conjunctions
Subordinating conjunctions introduce dependent clauses in traditional grammar.
Examples include because, although, if, when, while, and unless.
“I stayed home because I felt sick.”
“Although it was raining, we went outside.”
Correlative Conjunctions
Correlative conjunctions work in pairs.
Common examples include:
- Both … and
- Either … or
- Neither … nor
- Not only … but also
“Both Sarah and Emma attended the meeting.”
“Either call me or send a message.”
Common Conjunctions Chart
| Conjunction | Example | Function |
|---|---|---|
| And | Tea and coffee | Addition |
| But | Tired but happy | Contrast |
| Or | Tea or coffee | Choice |
| Because | Because I was sick | Reason |
| Although | Although it rained | Contrast |
| If | If you agree | Condition |
| When | When she arrived | Time |
| While | While I waited | Time or contrast |
Remember: Conjunctions connect grammatical units and help explain relationships between ideas.
Preposition vs. Conjunction Comparison Chart
Prepositions and conjunctions can express similar meanings, but they differ in their typical grammatical functions.
Main Comparison
| Question | Preposition | Conjunction |
|---|---|---|
| What is its main job? | Introduces a relational phrase | Connects grammatical units |
| What commonly follows it? | Noun phrase | Word, phrase, or clause |
| Can it show time? | Yes | Yes |
| Can it show place? | Often | Less commonly |
| Can it connect equal units? | Not usually | Yes, coordinating conjunctions |
| Example | Under the chair | The chair and the table |
| Example with before | Before dinner | Before dinner started |
Preposition Example
“The children played after school.”
The phrase after school tells us when they played.
Conjunction Example
“The children played after school ended.”
In traditional grammar, after introduces the dependent clause school ended.
Example With Both
“She studied in the library because she had an exam.”
Here:
- In is a preposition introducing the library.
- Because is a conjunction introducing she had an exam.
Why This Difference Matters
Understanding the structure helps you choose the correct expression.
Compare:
“She stayed home because of the rain.”
“She stayed home because it was raining.”
Both are correct, but the first uses a prepositional expression and the second uses a conjunction introducing a clause.
Writing tip: A sentence can contain both prepositions and conjunctions.
How to Identify a Preposition in a Sentence
To identify a preposition, examine the phrase it introduces and the relationship it expresses.
Test 1: Look for a Noun Phrase
“The book is on the desk.”
On introduces the noun phrase the desk.
Test 2: Look for a Relationship
“She arrived before noon.”
Before shows a time relationship.
Test 3: Look for Direction
“He walked through the tunnel.”
Through describes the route of movement.
Test 4: Look for Cause
“The match was canceled because of the storm.”
Because of is a complex preposition introducing the storm.
Test 5: Identify the Whole Phrase
“She sat beside her brother.”
The entire prepositional phrase is beside her brother.
Important Exception
Not every preposition must be immediately followed by a noun phrase.
For example:
“Who are you talking to?”
Here, to is a preposition whose complement appears earlier in the question.
Another example:
“She looked up.”
Depending on the grammatical analysis, up can be treated as a particle or an intransitive preposition.
Key rule: Identify the word’s grammatical function rather than relying only on its position.
How to Identify a Conjunction in a Sentence
A conjunction connects grammatical units or introduces a dependent clause.
Test 1: Look for Two Connected Words
“I bought tea and coffee.”
And connects two nouns.
Test 2: Look for Two Connected Clauses
“She was tired, but she continued working.”
But connects two independent clauses.
Test 3: Look for a Reason Clause
“I stayed home because I was sick.”
Because introduces a reason.
Test 4: Look for a Condition
“If you study, you will improve.”
If introduces a conditional clause.
Test 5: Look for a Paired Structure
“Either Sarah or Emma will present.”
Either … or connects alternatives.
Independent vs. Dependent Clauses
An independent clause can stand alone as a complete sentence.
Example:
“I stayed home.“
A dependent clause cannot normally stand alone as a complete sentence.
Example:
“Because it was raining.“
Combine them:
“I stayed home because it was raining.“
Important Grammar Note
Words such as before, after, since, and until are traditionally called subordinating conjunctions when they introduce clauses.
However, modern grammatical frameworks may classify these words as prepositions that take clause complements.
For everyday grammar learning, the traditional distinction is useful, but it is not the only accepted analysis.
20 Examples of Prepositions in Sentences
The following examples show common prepositions used for place, time, direction, and other relationships.
Prepositions of Place
- The keys are on the table.
- The cat slept under the chair.
- She stood beside her friend.
- The ball rolled behind the sofa.
- The store is between two buildings.
Prepositions of Time
- The meeting begins at noon.
- We arrived before dinner.
- She called after lunch.
- He has lived here since 2020.
- They talked during the break.
Prepositions of Direction and Movement
- She walked into the room.
- The children ran across the field.
- He drove toward the airport.
- We traveled through the mountains.
- The bird flew over the fence.
Other Common Prepositions
- She bought flowers for her mother.
- The match was canceled because of rain.
- He succeeded through hard work.
- The book was written by a historian.
- Everyone attended except Daniel.
Key takeaway: Prepositions can express place, time, movement, cause, purpose, agency, and exceptions.
20 Examples of Conjunctions in Sentences
These examples show coordinating, subordinating, and correlative conjunctions.
Coordinating Conjunctions
- I bought apples and oranges.
- She was tired, but she kept working.
- Would you like tea or coffee?
- He was hungry, so he made dinner.
- The task was difficult, yet she finished it.
Subordinating Conjunctions
- I stayed home because I was sick.
- Although it was raining, we went outside.
- If you practice, you will improve.
- Call me when you arrive.
- She listened while he explained the plan.
Time and Condition Conjunctions
- We left after the movie ended.
- Finish your homework before you watch TV.
- Wait here until the bus arrives.
- Since you are ready, we can begin.
- You can join us unless you have other plans.
Correlative Conjunctions
- Both Sarah and Emma attended.
- Either call me or send a text.
- Neither the manager nor the assistant was available.
- She is not only talented but also hardworking.
- I don’t know whether he will stay or leave.
Remember: Conjunctions connect ideas, introduce clauses, and help show relationships such as addition, contrast, reason, time, and condition.
Types of Prepositions in English Grammar
Prepositions can be grouped according to the relationships they express.
Prepositions of Place
These describe location.
Examples: in, on, under, beside, between.
“The bag is under the desk.”
Prepositions of Time
These describe when something happens.
Examples: at, on, in, before, after, during.
“The meeting starts at nine.”
Prepositions of Direction
These describe movement or direction.
Examples: to, into, toward, through, across.
“She walked toward the station.”
Prepositions of Cause
These describe reasons.
Examples: because of, due to, owing to.
“The flight was delayed because of fog.”
Prepositions of Manner or Means
These describe how something happens.
Examples: by, with, through.
“She opened the package with scissors.”
Simple and Complex Prepositions
A simple preposition is usually a single word, such as in, at, or under.
A complex preposition contains more than one word, such as because of, in front of, or according to.
| Type | Examples | Sentence |
|---|---|---|
| Place | Under, beside | Under the table |
| Time | Before, during | Before dinner |
| Direction | Into, toward | Into the room |
| Cause | Because of | Because of rain |
| Means | By, with | With a key |
| Complex | In front of | In front of the house |
Important: These are meaning-based groups. A single preposition can express different relationships in different sentences.
Types of Conjunctions in English Grammar
Traditional grammar divides conjunctions into three main categories.
Coordinating Conjunctions
These connect words, phrases, or clauses of equal grammatical status.
Examples include and, but, or, nor, yet, so, and for.
“She enjoys reading and writing.”
Subordinating Conjunctions
These introduce dependent clauses.
Examples include because, although, if, unless, when, and while.
“Although she was tired, she finished the project.”
Correlative Conjunctions
These work in pairs to connect matching grammatical structures.
Examples include:
- Both … and
- Either … or
- Neither … nor
- Not only … but also
“Both the teacher and the students were ready.”
Conjunction Types Chart
| Type | Common examples | Function |
|---|---|---|
| Coordinating | And, but, or | Connects equal units |
| Subordinating | Because, although, if | Introduces dependent clauses |
| Correlative | Either … or | Connects paired alternatives |
What About However and Therefore?
Words such as however, therefore, and moreover are often called conjunctive adverbs or linking adverbs.
They connect ideas in meaning but do not normally join independent clauses in the same way as coordinating conjunctions.
Correct:
“She was tired; however, she continued.”
Also correct:
“She was tired. However, she continued.”
Avoid joining two independent clauses with only a comma before however.
Comma Rules for Conjunctions
Rule 1: Use a comma before a coordinating conjunction joining two independent clauses.
“She studied hard, and she passed the test.”
Rule 2: Do not automatically add a comma when joining two words.
“I bought apples and oranges.”
Rule 3: Use a comma after an introductory dependent clause.
“Although it was raining, we went outside.”
Rule 4: A dependent clause after the main clause often needs no comma.
“We went outside although it was raining.”
These rules help prevent comma splices and unnecessary punctuation.
Words That Can Be Prepositions or Conjunctions
Some words have more than one grammatical use. Common examples are before, after, since, and until.
Before: Preposition vs. Conjunction
Preposition in traditional grammar:
“We arrived before dinner.”
Conjunction in traditional grammar:
“We arrived before dinner started.”
After: Preposition vs. Conjunction
Preposition:
“She called after lunch.”
Conjunction:
“She called after lunch ended.”
Since: Preposition vs. Conjunction
Preposition:
“He has lived here since 2020.”
Conjunction:
“He has lived here since he graduated.”
Until: Preposition vs. Conjunction
Preposition:
“We waited until midnight.”
Conjunction:
“We waited until the clock struck midnight.”
Comparison Table
| Word | Preposition use | Conjunction use |
|---|---|---|
| Before | Before the meeting | Before the meeting began |
| After | After lunch | After lunch ended |
| Since | Since Monday | Since the course began |
| Until | Until sunset | Until the sun set |
Why Grammar Books Sometimes Disagree
Traditional school grammar often uses the structure following the word to distinguish prepositions from subordinating conjunctions.
Some modern grammars instead classify words such as before, after, since, and until as prepositions in both uses.
For example:
“After lunch” contains a noun phrase complement.
“After lunch ended” contains a clause complement.
Under that modern analysis, after remains a preposition in both cases.
Important: These are different grammatical analyses, not evidence that one of the example sentences is incorrect.
Preposition vs. Conjunction: Clauses and Phrases
Understanding the difference between a phrase and a clause makes the traditional distinction easier.
What Is a Phrase?
A phrase is a group of words that functions as a grammatical unit. It does not necessarily contain a subject–predicate structure.
Example:
“After the meeting“
This is a prepositional phrase.
What Is a Clause?
A clause contains a subject and a predicate, usually including a verb.
Example:
“After the meeting ended“
The clause contains the subject the meeting and the verb ended.
Side-by-Side Comparison
| Phrase | Clause |
|---|---|
| Before dinner | Before dinner started |
| After school | After school ended |
| Since Monday | Since the course began |
| Until sunset | Until the sun set |
Why the Difference Matters
In traditional grammar, words such as before and after are often called prepositions before noun phrases and subordinating conjunctions before clauses.
However, not every conjunction introduces a clause.
For example:
“Tea and coffee”
Here, and joins two nouns.
Practical Comparison: Because vs. Because Of
“She stayed home because she was sick.”
The expression because she was sick contains a clause.
“She stayed home because of her illness.”
The expression because of her illness contains a prepositional phrase.
Key point: Phrase-versus-clause tests are useful for traditional subordinating conjunctions, but they do not explain every conjunction.
Common Preposition vs. Conjunction Mistakes
Writers sometimes confuse prepositions and conjunctions because certain words have similar meanings.
Common Mistakes Table
| Incorrect or awkward | Correct | Explanation |
|---|---|---|
| Because the rain, we stayed home. | Because of the rain, we stayed home. | Because of introduces a noun phrase |
| Because of it rained, we stayed home. | Because it rained, we stayed home. | Because introduces a clause |
| Despite it was cold, we went out. | Although it was cold, we went out. | Although introduces a clause |
| Although the rain, we played. | Despite the rain, we played. | Despite introduces a noun phrase |
| During I was studying, she called. | While I was studying, she called. | While introduces a clause |
| I was tired, however I continued. | I was tired; however, I continued. | Avoid a comma splice |
Mistake 1: Because vs. Because Of
Use because before a clause.
“I stayed home because I was sick.”
Use because of before a noun phrase.
“I stayed home because of the rain.”
Mistake 2: Although vs. Despite
Use although before a clause.
“Although it was cold, we went outside.”
Use despite before a noun phrase or an appropriate -ing construction.
“Despite the cold weather, we went outside.”
“Despite feeling tired, she continued.”
Mistake 3: During vs. While
Use during with a noun phrase.
“She called during the meeting.”
Use while to introduce a clause.
“She called while I was working.”
Mistake 4: Joining Independent Clauses Incorrectly
Incorrect:
“I was tired, I continued working.”
Correct:
“I was tired, but I continued working.”
Also correct:
“I was tired; however, I continued working.”
Mistake 5: Adding Unnecessary Commas
Unnecessary:
“I bought apples, and oranges.”
Better:
“I bought apples and oranges.”
When and joins two simple nouns, a comma is usually unnecessary.
Easy Memory Tricks
- Preposition: Think relationship.
- Conjunction: Think connection.
- Because + clause: Because it rained.
- Because of + noun phrase: Because of rain.
- During + noun phrase: During class.
- While + clause: While class continued.
Best tip: Look at the grammatical structure following the word, not only its meaning.
Preposition vs. Conjunction Practice Quiz
Choose the best answer using traditional school grammar.
Questions
1. Which word is a preposition in “The cat slept under the bed”?
A. Slept
B. Under
C. Cat
D. The
2. Which word is a coordinating conjunction in “She was tired, but she continued”?
A. Tired
B. Continued
C. But
D. She
3. Which sentence uses because correctly?
A. We stayed home because the rain.
B. We stayed home because it rained.
C. We stayed home because of it rained.
D. We stayed home because raining.
4. In “We arrived before sunset,” how is before traditionally classified?
A. Conjunction
B. Preposition
C. Pronoun
D. Noun
5. Which sentence uses during correctly?
A. During I studied, she called.
B. During she arrived, we left.
C. She called during the meeting.
D. During it rained, we waited.
6. Which sentence correctly joins two independent clauses?
A. She was tired, she continued.
B. She was tired, but she continued.
C. She was tired, however she continued.
D. She was tired because of she continued.
Answers and Explanations
1. B — Under. It introduces the noun phrase the bed and shows location.
2. C — But. It connects two independent clauses and shows contrast.
3. B — We stayed home because it rained. Because introduces a clause.
4. B — Preposition. In traditional grammar, before introduces the noun sunset.
5. C — She called during the meeting. During introduces a noun phrase.
6. B — She was tired, but she continued. The comma and coordinating conjunction correctly join the clauses.
Answer Key: 1-B | 2-C | 3-B | 4-B | 5-C | 6-B
Frequently Asked Questions
What is the main difference between a preposition and a conjunction?
A preposition typically introduces a phrase showing a relationship, such as under the table. A conjunction connects grammatical units, as in tea and coffee or because it rained. Some words have different classifications depending on the grammar framework.
Can a word be both a preposition and a conjunction?
Yes, in traditional grammar. Words such as before, after, since, and until are commonly called prepositions before noun phrases and subordinating conjunctions before clauses. Some modern grammars analyze them as prepositions in both uses.
Is because a preposition or conjunction?
Because is traditionally a subordinating conjunction when it introduces a clause, as in “because it rained.” Because of is a complex preposition, as in “because of the rain.” Informal uses such as “because science” also exist.
Is before a preposition or conjunction?
In traditional grammar, before is a preposition in “before dinner” and a subordinating conjunction in “before dinner started.” Modern grammatical analyses may classify both uses as prepositional.
What are five examples of prepositions?
Five common prepositions are in, on, at, under, and between. They can show relationships involving location, time, or position.
What are five examples of conjunctions?
Five common conjunctions are and, but, or, because, and although. They connect words, phrases, or clauses and express relationships such as addition, contrast, choice, and reason.
What is the difference between during and while?
During normally introduces a noun phrase, as in “during class.” While introduces a clause, as in “while the teacher was speaking.” Both can express time, but their grammatical structures differ.
How can I identify prepositions and conjunctions easily?
Look at the structure and function. A preposition often introduces a noun phrase that expresses a relationship. A conjunction connects grammatical units or introduces a dependent clause. Be careful with words such as before, after, since, and until, which have different analyses across grammar frameworks.
Conclusion and References
Understanding preposition vs. conjunction helps you build clearer and more accurate English sentences.
A preposition typically introduces a phrase showing a relationship involving place, time, direction, cause, or another meaning.
A conjunction connects words, phrases, or clauses and helps show relationships such as addition, contrast, reason, condition, and time.
The most useful beginner rule is to examine the structure following the word.
Compare:
- Before dinner — Traditionally a prepositional phrase.
- Before dinner started — Traditionally a conjunction introducing a clause.
Remember that modern grammatical frameworks sometimes classify these structures differently. The important skill is understanding how the word works in context.
Practice with real sentences, check whether the following words form a noun phrase or clause, and pay attention to common pairs such as because/because of, although/despite, and while/during.
Final memory rule: Prepositions express relationships; conjunctions connect grammatical units.