A semi-colon [;] is a bit like a ‘soft’ full stop; wherever you can place a semi-colon, you can also place a full-stop. The writer may decide to use a semi-colon when there is an extra piece of related information to give to the reader which is closely related to the sentence before, and which the writer feels does not really require a sentence of its own. It is, in other words, used to join two parts of a sentence that could otherwise be left as two sentences.
It is very important to note that a semi-colon can never be replaced by a comma but this is often an error that writers make. In the two following examples, we could not use a comma:
I looked long and hard for the right material; nothing else would do.
The whole team was looking exhausted; Maria was clearly showing the strain.
A semi-colon can also be used for complicated lists, in collaboration with commas. For example:
The research study explored a number of geographical areas: the southern parts of Wales, Scotland and Ireland; the northerly tip of the Hebrides; the most north-western tip of France.
A colon [:] is used to introduce a list, just as in the sentence above.
There are a number of possible solutions: medical, herbal or alternative.
The research team visited several sites: Larkness, Coaster and Ariemes.
A note on the use of however.
The word however is commonly used in academic writing and it is important to remember how it is used.
At the start of a sentence, it is normally followed by a comma.
However, Johansen’s later research was more productive.
When the word however appears in the middle of a sentence to introduce a contrast, it must follow a semi-colon and it must be followed by a comma.
The data suggest that foreign direct investment can have a significant affect on local industry; however, further research will be needed to confirm this finding.
The pattern of canals across the country provided a cheap and effective way to transport heavy goods for a hundred years; however, the development of a railway network would change all that.