There are two types of sentence error:
1 Writing an incomplete sentence, i.e. one that does not contain a subject
or a finite verb, or does not express a complete idea.
2 Writing two or more sentences with only a comma between them.
The most common error of sentence structure is joining two or more sentences
together with only a comma between them. People seem to do this less often
when the subjects of the sentences are different than when they are the
same. Fewer people would write:
• The client ran down the road, the supervisor ate a doughnut.
than
• He ran down the road, he was in a hurry.
A moment’s thought will show that the structure of both these ‘sentences’ is
identical and, if one is wrong, both are wrong.
1 The client  ran  down the road,
2 The supervisor ate a doughnut.
3 He  ran down the road.
4 He was in a hurry.
These mistakes happen because the writer feels that the sentences are too
short and that, as they belong together in meaning, they ought to be joined.
This may be true, but using a comma is not the way to do it.
Let us look again at the faulty construction:
• He ran down the road, he was in a hurry.
There are four ways of putting this right:
1 He ran down the road.  He was in a hurry.
2 He ran down the road; he was in a hurry.
3 He ran down the road because he was in a hurry.
4 Being in a hurry, he ran down the road.Write short, clear sentences
Business English favours the use of clear, short sentences. Short sentences
demand clarity of thought. Long sentences can easily become muddled and hard
for the reader to understand.
Make sure that every sentence you write deals with only one topic. This is
called the rule of unity. Whenever you complete a clear-cut,self-contained
statement, no matter how short it is, use a full stop.
A sentence should deal with one topic.
People often write long sentences that are not unities. They are long simply
because a number of separate statements, which should have had a sentence
each, have been bundled together. For example:
I looked out of the window to see what the weather was like and as it
was fine I decided to suggest that the clients should go out for a walk in
the gardens which were beautiful and had many interesting birds and
plants.
Try this!
Rewrite the passage using short, clear sentences. You can change the
wording if you wish.
Long sentences
Even a long sentence (one of 20 words or more) should be a unity. A good long
sentence is one whose different parts are so closely related that if a break
were made between them it would disturb the flow of thought.
Every sentence should be a unity.Try this!
Divide the following into several sentences, without altering the wording.
Thank you for your enquiry of 3
rd
 December concerning holidays in
Andalusia, we enclose a selection of brochures for you to look at, our
holiday packages are individually designed to suit customers’
requirements they can be supplied with either air or ferry travel to suit
your individual needs, our consultants will be pleased to meet with you to
discuss your requirements and put together an individual package for
you, we are able to make any arrangements required including those to
meet the needs of clients with mobility problems