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Combining Sentences To Show Relationships

Students learn to combine two simple sentences into compound or complex sentences using the right conjunction to show how ideas relate, such as cause, contrast, time, or condition.

Introduction

Short, simple sentences are easy to write, but a string of them can sound choppy and can hide how ideas connect. When you combine two simple sentences into one compound or complex sentence, you show your reader exactly how those ideas relate to each other, whether one idea causes another, contrasts with another, or happens before or after it.

Start With Two Simple Sentences

A simple sentence is one independent clause. It has a subject and a verb, and it expresses a complete thought on its own, such as "The rain started" or "We moved the picnic inside." On their own, these two sentences do not tell the reader how the two events are connected. Combining them turns two separate facts into one clear relationship.

Building Compound Sentences to Join Equal Ideas

A compound sentence joins two independent clauses that are equally important. You join them with a comma and a coordinating conjunction: "and," "but," "or," "so," "yet," "for," or "nor."

Example: "The rain started, so we moved the picnic inside." Both ideas keep equal weight, and the word "so" tells the reader that the second event happened because of the first.

Building Complex Sentences to Show Unequal Ideas

A complex sentence joins one independent clause with one dependent clause. The dependent clause starts with a subordinating conjunction, such as "because," "when," "although," "since," "before," or "after," and it cannot stand alone as a sentence.

Example: "Because the rain started, we moved the picnic inside." Here the subordinating conjunction "because" places more focus on the reason, and the dependent clause cannot work by itself. Changing from "so" to "because" changes which clause feels more important, even though the two sentences describe the same events.

Figure 1: Two simple sentences can become one compound sentence or one complex sentence, depending on the conjunction you choose.

Choosing the Right Conjunction for the Relationship

Before you combine two sentences, ask yourself what relationship you want to show. Different conjunctions signal different relationships.

For cause and effect, use "because," "since," or "so." For contrast, use "but," "yet," or "although." For time, use "when," "before," "after," or "while." For condition, use "if" or "unless." Picking the right conjunction matters as much as picking the right sentence type, since the wrong word can confuse the relationship even if the grammar is correct.

Step-by-Step: Combining Two Sentences

Follow these steps whenever you combine sentences in your own writing.

First, identify the two simple sentences and decide if the ideas are equally important or if one depends on the other. Second, choose a coordinating conjunction for equal ideas or a subordinating conjunction for a dependent relationship. Third, join the clauses with the correct punctuation: a comma before a coordinating conjunction, or a comma after an introductory dependent clause. Fourth, read the new sentence aloud to check that it clearly expresses the relationship you intended.

Example: Start with "I finished my homework" and "I watched a movie." Combined with time in mind: "After I finished my homework, I watched a movie." Combined with equal weight in mind: "I finished my homework, and I watched a movie."

Key Terms & Definitions

Simple Sentence: One independent clause that expresses a complete thought, such as "The storm ended."

Compound Sentence: Two independent clauses joined by a comma and a coordinating conjunction.

Complex Sentence: One independent clause joined with one dependent clause using a subordinating conjunction.

Coordinating Conjunction: A joining word such as "and," "but," "or," "so," "yet," "for," or "nor" that connects two equal ideas.

Subordinating Conjunction: A joining word such as "because," "when," "although," or "since" that starts a dependent clause.

Independent Clause: A group of words with a subject and a verb that can stand alone as a complete sentence.

Dependent Clause: A group of words with a subject and a verb that cannot stand alone and needs an independent clause to complete its meaning.

Related lessons

Choosing Sentence Types For Relationships