The Sentence

Sentence fragments are a group of words that don't contain all the elements necessary to create a sentence and so should not stand alone. Sentence fragments are usually incomplete ideas;

for example:

Although it had not rained for months. ????? x

This sentence does not convey a complete idea. If these words were spoken to you, you would wait for the person to tell you the other half of the idea:

Although it had not rained for months, there was still no shortage of water. 

Incorrect: When they are heated. x (fragment)

Correct: Solids turn into liquids when they are heated. (complete idea) 

Incorrect: Despite the fact he had little money. x (fragment)

Correct: He managed to pay his rent despite the fact he had little money. (complete idea) 

A run-on sentence is a sentence which includes more than one complete idea: it is actually a series of sentences run together that are joined by commas instead of full stops.

Incorrect punctuation can result in run-on sentences.

Team leaders should be aware of group norms, they should try to find out which norms are task-related and which are counter-productive. x

The two parts of this single ‘sentence’ should be separated to make two complete sentences or should be joined by a semicolon instead of a comma.

Team leaders should be aware of group norms. They should try to find out which norms are task-related and which are counter-productive. 

Team leaders should be aware of group norms; they should try to find out which norms are task-related and which are counter-productive. 

Summary:

Run-on sentences occur when complete stand-alone ideas have not been properly punctuated as sentences.

They can be fixed by either:
- re-punctuating and making two separate sentences
- creating a ‘which’ or ‘who’ clause

Run-on sentence:

Passive euthanasia is withdrawing or withholding lifesustaining treatment from a terminally ill and suffering
patient, it seems more easily justified than killing such a patient. ×

Correct (version 1 – new sentence)

Passive euthanasia is withdrawing or withholding lifesustaining treatment from a terminally ill and suffering
patient. This seems more easily justified than killing such a patient. 

Correct (version 2 – ‘which’ clause)

Passive euthanasia, which is withdrawing or withholding lifesustaining treatment from a terminally ill and suffering patient, seems more easily justified than killing such a patient. 

To be a fully grammatical sentence, the subject and the verb in the sentence need to ‘agree’ in number (plural/singular).

Example:

The article by Smith and Jones (2001) discusses the impact of the internet on society. 

The singular subject of this sentence ‘the article’ requires a singular verb ‘discusses’ if they are to ‘agree.’

Incorrect: Smith et al. (2004) believes this is not the case. 

Correct: Smith et al. (2004) believe this is not the case.

(plural subject - Smith et al.- and so plural verb) 

Incorrect: Health problems occurs as a result. 

Correct: Health problems occur as a result. 

Punctuation

Reading your sentences aloud is a good way of checking whether they are easy to understand. If you run out of breath, then they are probably too long and may need to be broken up with appropriate punctuation, or split into two.

Example of unclear sentence:

The government proposes to increase the minimum purchase price for alcoholic products with the assumption that this should make alcohol more expensive thereby resulting in reducing alcohol units purchased which will in turn reduce the number of alcohol units consumed which should help address the problem.

This is difficult to make sense of. Using appropriate punctuation will help. It may also be necessary to reorganize some of the clauses.

Improved version:

The government proposes to increase the minimum purchase price for alcoholic products, with the assumption that this should make alcohol more expensive. This will result in a reduction in alcohol units purchased which will in turn reduce the amount of alcohol units consumed. This, therefore, should help address the problem.