Grammar Skills

Sentence structure

This guide explains how sentences are constructed and how different types of sentences are formed. It shows you how to punctuate each type correctly and how to combine different sentence types for effective written communication.

What is a complete sentence?

Sentences provide us with the framework for the clear written expression of our ideas. The aim in writing is always to write in complete sentences which are correctly punctuated. Sentences always begin with a capital letter and end in either a full stop, exclamation or question mark. A complete sentence always contains a verb, expresses a complete idea and makes sense standing alone.

Andy reads quickly. This is a complete sentence as it contains a verb (reads), expresses a complete idea and it does not need any further information for the reader to understand the sentence.

When Andy reads is an incomplete sentence. It contains a verb, but the opening word when tells us that something happens when Andy reads; we need more information to complete the idea.

When Andy reads, he reads quickly. This is now a complete sentence, as the whole idea of the sentence has been expressed. The following examples show the incomplete sentences in italics.

There is another theory. Which should not be ignored.

There is another theory which should not be ignored.

The proposal was finally rejected. Although they considered it.

Although they considered the proposal, it was finally rejected.

To check that you are writing in complete sentences, try reading your sentences aloud, pausing as indicated by the punctuation.Can each sentence stand alone as a complete thought?Iffurther information is needed to complete the idea, then it is not a complete sentence.

Types of sentences

As well as being able to write in complete sentences, it is important to be able to use a variety of sentence types that are correctly punctuated.

Sentences are made up of clauses: groups of words that express a single idea.There are two types of clauses: independent clauses and dependent clauses.Independent clauses can stand alone as complete sentences.A dependent clause needs an independent clause to complete its meaning.Different types of sentences are made up of different combinations of these two types of clauses.

Simple sentences consist of just one independent clause; it requires only one punctuation mark at the end (a full stop, exclamation or question mark).

The essay was late.

Compound sentences are made by joining simple sentences.We join sentences which are closely related in content to make the writing more fluid.We can join simple sentences with a comma and a word such as: and, but, so, yet.

The essay was late, so he lost marks.

We can also join simple sentences with a semi-colon.

The essay was late; he lost marks.

Complex sentences are made when we combine an independent clause with a dependent clause.The dependent clause in the following example is in italics.

Because his essay was late, he lost marks.

When the dependent clause comes first, as in the example above, it is separated from the independent clause with a comma.When the sentence begins with the independent clause, there is no need to separate the clauses with a comma.

He lost marks because the essay was late.

Comparing these two examples, it can be seen that the emphasis tends to fall on the clause at the beginning of the sentence.Vary your placement of dependent clauses in order to emphasise the most important idea in the sentence. Common ways to begin a dependent clause are: although, as, because, even though, if, instead, through, when, whenever, where, while.

Whilst more than one dependent clause can be used in a sentence, they must always be combined with an independent clause to complete the idea. Again, the dependent clauses in this example are in italics.

Although there are many dissenters, many of whom were prominent citizens, the policy still stands today.

Different types of sentences can be combined to form compound-complex sentences. In the example below, the central independent clause combines two sentence types.It serves as both the ending of the complex sentence and the beginning of the compound sentence.

When considering owning a pet, you must calculate the cost, or the animal may suffer.

When punctuating a compound-complex sentence, apply the rules for both compound and complex sentences. The example above begins with a dependent clause separated from the central clause by a comma, as in the rule for complex sentences.At the end of the sentence the independent clause is joined by a comma and the word or, as in the rule for the compound sentences.

Using different sentence types

Once you are aware of the different types of sentence construction,you can then choose and correctly punctuate the most helpful type of sentences for the expression of your idea.

The following series of short sentences, whilst grammatically correct, are jerky and abrupt.

Jackie is confident. She is a good speaker.She is considered to be an excellent presenter.Everyone finds her interesting. No one has been critical. She is supportive of others.

These sentences can be combined to make more fluid writing by combining sentences which are closely related,using the rules described earlier.

Jackie is confident, andshe is agood speaker. She is considered to be an excellent presenter.Everyone finds her interesting, and no one has been critical as she is supportive of others.

The following sentence is overly long and complicated. By shortening sentences that could confuse the reader,you can make the writing easier to follow.

If you consider buying a puppy, whatever age or breed, always consider the type of house you have, as this is the most important first step, because without considering this first you can find yourself with a dog that, despite your good intentions, you just cannot keep.

If you consider buying a puppy, whatever age or breed, always consider the type of house you have. This is the most important first step. Without considering this first, you can find yourself with a dog that you just cannot keep, despite your good intentions.


Use these guidelines to identify types of sentence construction in your own writing.To check the clarity of your sentence structure, try reading the writing aloud, stopping as indicated by the punctuation. Does each sentence stand on its own as a complete idea?Use the guidelines to either break an overly long sentence into shorter sentences, or join abrupt sentences together to make the writing more fluid.Varying the length and type of sentences whilst ensuring correct punctuation will improve the clarity of your written expression.

Using paragraphs

This guide explains how to make effective use of paragraphs in your writing. The function and features of a paragraph are explained, together with guidelines for using paragraphs to create a clear and coherent written structure.

What is a paragraph?

Writing of any length requires subdivision into a number of points or stages, and these stages are expressed in a paragraph. Paragraphs, whether denoted by a new line and an indentation or a line break, provide a structure for your writing. The end of a paragraph represents a significant pause in the flow of the writing. This pause is a signpost to the reader, indicating that the writing is about to move on to a different stage.Each paragraph should deal with one idea or aspect of an idea, and it should be clear to the reader what this main idea is.

How long should a paragraph be?

There is no absolute rule: very short or long paragraphs can work when used by an experienced writer. However, as a guideline, paragraphs should usually be no less that 2 or 3 sentences long and there should be 2 or 3 paragraphs per page of A4. The length of a paragraph depends on the idea being treated, but if a paragraph is shorter than 2 or 3 sentences, check to see if it is not really part of the previous or next paragraph. If your paragraph is longer than half a page, check to see if the idea wouldbe better explained in two or more paragraphs.

When do I start a new paragraph?

Start a new paragraph for each new point or stage in your writing. When you begin a paragraph you should always be aware of the main idea being expressed in that paragraph. Be alert to digressions or details that belong either in a different paragraph or need a paragraph of their own.

How do I write a paragraph?

A paragraph can have an internal structure with an introduction, main body and conclusion in the same way as an essay The example below shows a paragraph which:

  • introduces the paragraph's main point;
  • develops and supports the point;
  • shows the significance of the point made.

Grammar Skills Example Paragraph1

The previous example showed one style of paragraph. It is a useful rule always to have three stages in a paragraph: introduction, development and conclusion.

The introduction

The introduction makes the purpose of the paragraph clear so the reader can read the paragraph with this purpose in mind. It is usually necessary to show the place the paragraph has in the structure of the piece as a whole. This can be done with just a word (Nevertheless, However, Furthermore) or it may need a phrase (Another point to consider is....). In an essay, this might mean showing how the main idea of the paragraph answers the essay question. In some cases when the paragraph begins a new section, it may be necessary to write a separate paragraph which explains how the following section relates to the piece as a whole.

The development

The body of the paragraph should develop the idea that has been introduced at the beginning of the paragraph. This can be done by:

  • redefining the idea;
  • giving examples;
  • commenting on evidence;
  • showing implications or consequences;
  • examining opposing ideas.

The conclusion

The end of the paragraph can show the significance of the point, link back to the beginning of the paragraph, comment on the implications of the point as a whole, or make a link to the next paragraph. It is important not to end the paragraph with a digression or irrelevant detail. Each sentence in the paragraph should be part of the internal structure.

Another example of a paragraph using this three part structure is given below.

Grammar Skills Example Paragraph2


Paragraphs provide astructure for your writing which enables the reader to identify and follow the developing stages in your treatment of the material. Remember that paragraphs should have their own internal structure whilst fitting into the larger structure of the whole piece of writing. Be clear what the main idea for each paragraph is, deal with it as fully as is necessary for your purpose, but be alert to digression or irrelevancies.Check your own use of paragraphs by reading the first sentence to see if it outlines the paragraph's main idea. The effective use of paragraphs can be seen in writing when the reader can gain an overview of the content by reading the first sentence of each paragraph.

Using the apostrophe

This guide has been written to give a simple explanation of the use of the apostrophe (’). It explains the main rules for its use, and gives examples of commonly encountered problems.

The apostrophe has two main uses

  • It replaces missing letters when we join words e.g. I can't swim

This is known as a contraction.

  • It shows ownership e.g. this is John’s book.


When contractions are used, the apostrophe replaces the letter or letters that were removed to make a shorter word:

do not becomes don’t .

The apostrophe replaces the missing letter, in this case the o .

Further examples are:

I will becomes I’ll

you are becomes you’re

they are becomes they’re

Whilst it is important to understand the function of contractions, their use is not usually appropriate in academic writing.


Apostrophes are also used to show ownership - they make a word possessive. To make a word possessive follow the three simple rules given below.

1. If the word is singular add ’s

the student’s books-meaning the books belonging to the student.

Further examples are:

the boss’s armchair; the government’s legislation.

2. If the word is a plural but does not end ins add ’s :

women’s rights - meaning the rights of women.

Further examples are:

children’s playground- meaning the playground for children;

men’s changing rooms -meaning the changing rooms for men.

3. If the word is plural and ends in s just add an apostrophe:

the studentslibrary books-meaning the books belonging tothestudents.

Further examples are:

the ladies football league;the workersrights.

Common problems in using apostrophes

The apostrophe is frequently misused. Words that cause particular problems are:its / it’sandwhose / who’s.

Its / it’s

Use its when you want to show possession:

the government abandoned its policy.

Its belongs to a group of words that are already possessive. Other examples are: it is hers; it is yours. These words are already possessive; they do not need apostrophes to indicate possession.

Use it’swhen you want to shorten it is:

it’s a nice day.

It’sis a contraction of it is. The apostrophe replaces the missing i.

Whose / who’s

Use whose when you want to show possession:

the student whose notes I borrowed.

Whose belongs to the same group of possessive words as its. It does not need an apostrophe to denote possession.

Use who’s when you want to shorten who is:

the student who’s coming to visit.

Who’s is a contraction of who is. The apostrophe replaces the missing i.

Remember: just because a word ends in s, it does not mean it needs an apostrophe!An apostrophe is added to show possession or to replace a missing letter or letters in contractions. If you are unsure when to use an apostrophe, check your use of the apostrophe falls under one of the rules outlined in this guide.

Using the comma

This guide explains how the comma (,) can be used to make your writing clear, unambiguous and easy to read. It gives examples of the main uses of the comma, and highlights some commonly encountered problems.

Why use commas?

Commas are used to divide or separate parts of a sentence in order to make the meaning clear and the sentence easier to read. They mark a brief pause in the sentence, usually at a point where you would naturally pause if you were speaking rather than writing. They may be used to separate individual words or phrases within the sentence. Some examples of the main types of usage are given below.

Using commas to separate items in a list

Commas are used to separate the individual words or phrases that together make up a list.

The fish kept in the ponds were eels, tench, pike, perch and carp.

The main reasons for the closure were low enrolment, poor learningmaterial,staff recruitment problems and inadequate funds.

Note that a comma is not normally used before the last item in the list, unless it is needed for clarification.

The choices were History and Archaeology, Archaeology and Sociology, and Ancient History.

Here, a comma is used before the last item in the list to avoid confusion.

Separating the parts of a sentence

Commas are used to separate an introductory word or phrase from the main sentence, or to separate a word or phrase that briefly interrupts the flow of the sentence. In the examples below, the introductory and interrupting words or phrases have been italicised.

Nevertheless, many critics see value in this theory.

After the first decade, the changes were fully integrated into the system.

Numerous studies, however, prove that the theory is inaccurate.

The same theory, according to most writers, can be applied to language acquisition.

Similarly, commas are used to separate an afterthought or a final phrase that contrasts with the main part of the sentence.

The war was vitally important for Europe, far more than it was for Britain.

To understand a particular culture we must look at the whole of society, not just its individual parts.

A single sentence can, of course, use commas in more than one way. In the following example, commas are used to separate an introductory phrase, punctuate a list and separate a final contrasting phrase.


To use the comma effectively, avoid overuse as this can make the sentence difficult to read and understand. Use the comma purposefully, as shown in the example above, and re-read alonger sentence to check the pauses are in the most helpful places.

Using commas to link simple sentences

A series of short, simple sentences can be jerky and tedious to read.

The University is large. It is close to the town centre. There are special rooms available. Advance reservation is necessary.

A way of improving the flow of the writing is to link sentences with a comma

together with a linking word (a co-ordinating conjunction) such as and, but,

so, or, nor or yet.

The University is large, and it is close to the town centre. There are special rooms available, but advance reservation is necessary.


A comma cannot be used on its own to join two sentences. A comma only indicates a pause in a sentence; it can not join sentences without the addition of a co-ordinating conjunction. For example, these two sentences, whilst grammatically correct, would read better if joined.

The people followed their own creed. They were willing to die for it.

However, they can not be joined by using a comma on its own, as the comma shows only a pause, not a link.

X The people followed their own creed, they were willing to die for it. X

A comma together with a co-ordinating conjunction joins the sentences correctly.

The people followed their own creed, and they were willing to die for it.

Sentences can sometimes be joined effectively using a semi-colon (;). The companion leaflet, Using the Semi-colon and Colon provides a guide to its use.


If in doubt about your use of commas, read each sentence aloud, pausing briefly at each comma. If the sentence flows badly and seems jerky, you probably have too many commas. If you are breathless by the time you have reached the end of the sentence, you might need to insert some commas at appropriate points as shown in this guide. It may even be necessary to divide a very long sentence into two or more separate sentences.

Using the semi-colon and colon

This guide has been written to give a simple explanation of the use of the semi-colon (;) and colon (:). It explains how they can be used effectively and gives examples of their main uses.

The semi-colon

The semi-colon represents a break within a sentence that is stronger than a comma, but less final than a full stop. It enables the writer to avoid over use of the comma and preserves the finality of the full stop. Semi-colons are used to separate items in a list and to link closely related sentences.

To separate items in a list

Use the semi-colon to separate items in a list when one or more items contain a comma. (These examples use a colon to introduce items in the list. An explanation of the use of the colon is given below.)

The speakers were: Dr Sally Meadows, Biology; Dr Fred Eliot, Animal Welfare; Ms Gerri Taylor, Sociology; and Prof. Julie Briggs, Chemistry.

The four venues will be: Middleton Hall, Manchester; Highton House, Liverpool; Marsden Hall, Leeds; and the Ashton Centre, Sheffield.

The main points in favour of the system were that it would save time for buying, accounts and on-site staff; it would be welcome by the reception staff; it would use fewer resources; and it would be compatible with earlier systems.

To link sentences which are closely related

Closely related sentences are often linked to emphasise their relationship and to vary the pace of the writing. For example:

I read the book in one evening. It was not very helpful.

One way to link these sentences is with a comma and a word such as and, or, but, nor, for, so, yet (called co-ordinating conjunctions).

I read the book in one evening, but it was not very helpful.

For variety in sentence structure, the semi-colon can be used to link closely related sentences instead of a co-ordinating conjunction and comma.

I read the book in one evening; it was not very helpful.

The semi-colon tells the reader that the second clause is closely linked to the first clause. Note how sentences joined in this way are similar in either theme or grammatical structure as shown in the example below.

Personal writing utilises the first person form; impersonal writing utilises the third person form.

He was nervous about giving the speech; he asked for water several times.

The deadline has come forward a week; everyone's help will be needed.

For use with otherwise, however, therefore…

The semi-colon can be used to link sentences which also use words such as otherwise, however, therefore, as connectors. These connectors (known as conjunctive adverbs) also include: moreover, nevertheless, thus, besides, accordingly, consequently, instead, hence.

I did not finish reading the text; instead, I watched the news.

(Notice that the connecting word instead is followed by a comma).

The research is far from conclusive; nevertheless, it has some value in this case.

Dr Suptri argues that the research shows an increase in such occurrences; however, many experts would dispute this.

The colon

The colon acts as a pause which introduces related information. It indicates that the reader should look forward to information that follows on from the earlier statement. Some of the main ways a colon can be used are shown below.

To introduce a list

The colon can be used to introduce the items in a list.

Topics discussed will include: the structure of viruses, virus families and current concerns in virology.

Students joining the department undertake to: attend all lectures and tutorials, meet deadlines for written work and contribute to tutorials and seminars

To introduce an explanation, conclusion or amplification

The colon can also be used to introduce an explanation, conclusion or amplification of an earlier statement. The use of the colon separates and highlights the second statement, showing that it follows on from the first.

Tai chi is more than a form of physical exercise: it is meditation in movement.

After extensive research, the committee came to its conclusion: development could not take place without further funding.


The semi-colon and colon are often underused, yet their correct use can enhance the clarity of your writing. Beware of an over dependence on the comma and full stop, as this can make for ambiguous and repetitive sentence structure. Look in your writing for opportunities to use the semi-colon and colon in the ways described in this guide.

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