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Sentence problems: Run-on sentences and comma splices

Run-on sentences are a very frequent type of sentence problem. A good way of learning how to spot them, and fix them, is to understand what counts as a complete sentence.

Run-on sentences occur when a main clause is directly followed by another main clause in the same sentence, without the correct punctuation: either with no punctuation at all, as in example (1a), or with a comma to separate two main clauses, as in (1b) (this latter type is often called a comma splice). These errors can be fixed by using a full stop or a semicolon instead of a comma (1c–1d), or by re-writing with another type of linking word (1e). 

Incorrect:

(1a) Engineering was not something that interested me academically however that changed two years ago when I was first introduced to the Python programming language.

Incorrect (comma splice):

(1b) Engineering was not something that interested me academically, however that changed two years ago when I was first introduced to the Python programming language.

Correct (suggestions):

(1c) Engineering was not something that interested me academically; however, that changed two years ago when I was first introduced to the Python programming language.

(1d) Engineering was not something that interested me academically. However, that changed two years ago when I was first introduced to the Python programming language.

(1e) Engineering was not something that interested me academically, but that changed two years ago when I was first introduced to the Python programming language.

Even if you don't have a linking word such as however, you can still have a run-on sentence, as in (2a–b). In most cases, this can be fixed by adding a linking word such as as, while, or since (2c), or by ending the sentence with a full stop and beginning a new sentence (2d): 

Incorrect:

(2a) It is important for scientists to communicate clearly they need to be transparent about their work.

Incorrect (comma splice):

(2b) It is important for scientists to communicate clearly, they need to be transparent about their work.

Correct (suggestions):

(2c) It is important for scientists to communicate clearly as they need to be transparent about their work.

(2d) It is important for scientists to communicate clearly. This is because they need to be transparent about their work.

How do I spot a run-on sentence?

In (1a), (2a), and (3a) it would be possible to insert a full stop after the words academically, clearly, and questions, respectively. The rule is: if you can have a full stop, do not simply leave the punctuation out, and do not use a comma instead.

Run-on sentences with the word 'see' when referring to figures and tables

Note that a run-on also occurs when you put a comma before the phrase see Table/Figure X:

Incorrect:

(3a) The framework was used as a template for designing the questions, see Table 2. 

Why is this a run-on sentence? The reason is that the word see in this case is an imperative (i.e. you are asking the reader to do something). Imperatives form a type of full sentence, even though there is no subject. This problem can be fixed in several ways:

Correct (suggestions):

Use parentheses:

(3b) The framework was used as a template for designing the questions (see Table 2)

(3c) The framework was used as a template for designing the questions (Table 2).

Use a semicolon:

(3d) The framework was used as a template for designing the questions; see Table 2.

Re-phrase:

(3e) The framework shown in Table 2 was used as a template for designing the questions.

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Innehållsansvarig:Susanna Zeitler Lyne
Tillhör: Institutionen för lärande
Senast ändrad: 2023-06-26