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Learn Index · Grammar and Conventions Grade 3–5

Conjunctions and prepositions

Conjunctions join words or ideas; prepositions show how a noun relates to another word, such as where it is.

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Two kinds of connecting words

Some small words have big jobs. Conjunctions and prepositions connect ideas and show how they relate. Using them well helps you write longer, smoother and clearer sentences.

Part 1: Conjunctions

A conjunction is a joining word. It can join words, phrases or whole sentences.

Coordinating conjunctions: FANBOYS

A coordinating conjunction joins parts that are equally important. Remember them with FANBOYS:

Conjunction Use Example
For gives a reason She smiled, for she had won.
And adds information I like apples and pears.
Nor adds a negative He doesn’t swim, nor does he skate.
But shows contrast It was sunny, but it was cold.
Or shows a choice Do you want juice or milk?
Yet shows a surprising contrast He was tired, yet he kept running.
So shows a result It rained, so we stayed inside.

Making compound sentences

Join two complete sentences with a comma plus a FANBOYS word to make a compound sentence.

The bell rang. We went to recess. →
The bell rang, so we went to recess.

Remember: comma before the conjunction when it joins two complete sentences.

Subordinating conjunctions

A subordinating conjunction starts a part of a sentence that cannot stand alone. It shows relationships like time, cause or condition.

Common ones: because, when, although, if, since, after, before, while, unless, until

  • We stayed inside because it was raining.
  • When the bell rings, line up at the door.
  • Although I was tired, I finished my homework.
  • You can play if you finish your chores.

Comma tip: if the subordinating conjunction starts the sentence, put a comma after that part. Because it was raining, we stayed inside. If it is in the middle, you usually do not need a comma.

Part 2: Prepositions

A preposition shows how a noun or pronoun relates to another word in the sentence. Many prepositions tell where or when.

Prepositions of place

in, on, under, over, above, below, beside, between, behind, in front of, near, inside, outside, through, across, around

Think of a cat and a box. The cat can be in the box, on the box, under the box, beside the box, behind the box, jumping over the box. Almost anything a cat can do with a box is a preposition!

Prepositions of time

before, after, during, until, since, at, on, in

  • at 3 o’clock
  • on Monday
  • in July
  • during the movie
  • after lunch

Other prepositions

with, without, about, for, from, to, of, by, like

I went with my mom. This book is about sharks. The gift is from Grandpa.

Prepositional phrases

A prepositional phrase begins with a preposition and ends with a noun or pronoun, which is called the object of the preposition.

  • under the bridge
  • after school
  • with my best friend
  • across the busy street

Prepositional phrases add details about where, when and how: The puppy slept on the couch after dinner.

Same word, different job

Some words, like before, after and since, can be prepositions or conjunctions.

  • We ate after the game. (preposition; followed by a noun)
  • We ate after the game ended. (conjunction; followed by a subject and verb)

How to use these words in your writing

  1. Combine choppy sentences with FANBOYS or subordinating conjunctions.
  2. Show relationships clearly: because for reasons, but for contrasts, so for results.
  3. Add detail with prepositional phrases.
  4. Vary your sentence beginnings: start some sentences with a prepositional phrase or subordinating conjunction.

Worked examples

Example 1: Combine. I wanted to go outside. It was raining.
I wanted to go outside, but it was raining.

Example 2: Combine with a subordinating conjunction. We cheered. Our team scored.
We cheered when our team scored.

Example 3: Find the prepositional phrase. The kite got stuck in the tall tree.
in the tall tree (preposition: in; object: tree).

Example 4: Add detail. The dog barked.
The dog barked at the mail carrier through the window.

Common mistakes

  • Missing comma in compound sentences. It was late so we went home → It was late, so we went home.
  • Starting with a fragment. Because I was hungry. is not a complete sentence. Add the main part: Because I was hungry, I ate a snack.
  • Overusing “and”. Try other conjunctions to show clearer relationships.
  • Wrong time preposition. in Monday → on Monday; on July → in July.

Try it yourself

  1. Combine with a FANBOYS conjunction: I studied hard. I passed the test.
  2. Combine using although: It was cold. We went swimming.
  3. Circle the prepositions: The cat hid behind the curtain during the storm.
  4. Choose: We have a test (on / in) Friday.
  5. Add a prepositional phrase: The children played.

Answers: 1. I studied hard, so I passed the test. 2. Although it was cold, we went swimming. 3. behind, during. 4. on. 5. Example: The children played in the park after school.

Study tip

Write FANBOYS on a sticky note on your desk. When you revise, look for two short sentences that could be joined with one of them.

Quick recap

  • Conjunctions join words, phrases and sentences.
  • FANBOYS are coordinating conjunctions; use a comma before them in compound sentences.
  • Subordinating conjunctions like because and when show time, cause and condition.
  • Prepositions show place, time and relationships.
  • Prepositional phrases add detail to sentences.