Why should sentence run-ons be avoided in EAP?

This is the first of two lessons about Sentence Run-Ons and Fragments. To complete this course, read each lesson carefully and then unlock and complete our materials to check your understanding.   

– Review the four sentence structures in English grammar

– Introduce the concept and classification of sentence-runs

– Provide advice for how to avoid and fix sentence run-ons

Lesson 1

The skill of writing clear, concise, accurate and grammatical sentences that demonstrate a variety of sentence structures can be somewhat challenging for learners of English, particularly when using English for Academic Purposes (EAP). This short two-lesson course on sentence run-on and fragments therefore discusses the most common errors when attempting to correctly form sentences. While a short review of the four sentence structures has been provided below, students may wish to first study our short courses on simple and compound sentences and compound and compound-complex sentences to improve their knowledge.  

Reviewing the Four Sentence Structures

  • Simple Sentences: This sentence structure requires one independent clause only, such as in the expression ‘I study English’. This example clause has a subject ‘I’ and a main verb ‘study’ as minimum phrase functions and can stand alone as a complete sentence. Other functions such as objects, adverbials and complements are also possible in simple sentences.
  • Compound Sentences: Compound Sentences require two or more independent clauses, such as in the expression ‘We study English, and we enjoy studying it’. Generally, independent clauses are joined together in compound sentences using a combination of coordinate conjunctions such as ‘and’ or ‘but’ and commas (,).
  • Complex Sentences: Sentences which are complex require one or more independent clauses and one dependent clause to be grammatical. As in the expression ‘I study English because I like it’, dependent clauses are usually introduced with subordinate conjunctions such as ‘because’ or ‘even though’. Such dependent clauses cannot stand alone as complete thoughts and must eventually connect with an independent clause.
  • Compound-Complex Sentences: Finally, compound-complex sentences are a combination of compound and complex sentence structures. This sentence type requires two or more independent clauses and one or more dependent clauses, all of which are joined with a combination of coordinate and subordinate conjunctions, such as in the example ‘Because I like the English language, I study it every day, and I study it alone and with teachers’.

What are Sentence Run-Ons?

Now that you can hopefully recognise and use simple, compound, complex and compound-complex sentence structures in your own writing, it’s important to next turn our attention to the types of error that are common among students when writing sentences. The first major error type is called a run-on (or fused) sentence. Such run-on sentences have two or more clauses of any type that have been joined incorrectly – as in the following examples:

In example (a), the dependent clause ‘even though I don’t find it interesting’ has been joined to the following independent clause without using a comma (,) making an ungrammatical complex sentence. Likewise, in example (b), two independent clauses have been combined into a compound sentence by using only a single comma, creating what’s known as a comma splice. Joining two independent clauses in this way is ungrammatical and should always be avoided by students.

Thankfully, and as can be seen in the examples below, there are two simple ways of fixing each sentence. In example (a), we can simply add a comma between the dependent and independent clauses or inverse the order of those clauses, while in example (b), we can add a coordinate conjunction between the two independent clauses or replace the comma with a semicolon (;):

Where things become more complicated is when using compound-complex sentences, as these constructions may be of almost any length and still be grammatical (although overly long sentences are admittedly difficult to understand). Whether a sentence is considered to be a run-on is therefore not generally to do with its length but with whether that sentence uses incorrect or absent conjunctions and punctuation. With this in mind, there are generally three ways in which students tend to create sentence run-ons instead of grammatical sentences, and students should learn to avoid each of these:

In scenario 1, when conjunctive adverbs such as ‘however’ and ‘therefore’ are used to join two independent clauses, a semicolon (;) should be placed before the adverb and a comma (,) after it. Scenarios 2 and 3 are somewhat different, however. Both of these scenarios involve comma splices in which a comma has been incorrectly used to join two independent clauses – which is a common enough student error. Thankfully, a combination of the appropriate conjunction and/or punctuation mark can usually fix such errors with ease.

Now that you’ve completed the first half of this short course on sentence run-ons and fragments, you might wish to attempt Lesson 1’s activities to check your progress. Following this, it’s recommend that you continue on to Lesson 2 which focuses specifically on sentence fragments.

1 of 2 Lessons Completed


Once you’ve completed both lessons in this short course about Sentence Run-Ons and Fragments, you might then wish to download our Lesson Worksheets to check your progress or print for your students. These professional PDF worksheets can be easily accessed for only a few Academic Marks.

Lesson 1 explores the topic: Why should sentence run-ons be avoided in EAP? Our Lesson 1 Worksheet (containing guidance, activities and answer keys) can be accessed here at the click of a button. 

Lesson 2 explores the topic: How can I fix ungrammatical sentence fragments? Our Lesson 2 Worksheet (containing guidance, activities and answer keys) can be accessed here at the click of a button. 

To save yourself 1 Mark, click on the button below to gain unlimited access to all of our Sentence Run-Ons and Fragments Lesson Worksheets. This All-in-1 Pack includes every lesson, activity and answer key related this topic in one handy and professional PDF.


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