Learning outcomes

Semi-colons
A semi-colon can be used to separate two main clauses in a sentence instead of a conjunction or comma. It is most suitable when the clauses are closely related in meaning. The following sentences make perfect sense when joined together in this way.
I enjoyed the concert; it was a pleasure to be there.
Some students are well organised with assignments; others leave them until the last minute.
There may also be times when the semi-colon indicates the relationship between two sentences.
Sam vacuumed the floor for the third time.
The party had been a great success.
If this becomes Sam vacuumed the floor for the third time; the party had been a great success, the relationship between the two can be inferred.
Semi-colons can also be used to separate items in a list, usually when these items consist of longer phrases or where commas would not make separations clear enough, as in our earlier example of jacket potato toppings.
He packed a large jar of yeast extract; a jar of his favourite marmalade; several tins of baked beans; the largest box of tea he could find; and a packet of digestive biscuits.
Once children know how to use them, semi-colons can add a level of sophistication to their writing
Dashes and brackets
Dashes and brackets perform similar functions and can be used to replace colons, semi-colons and commas. While a colon and semi-colon often suggest a link between the two parts of the sentence, dashes and brackets can be less connected. They are useful for separating off parts of a sentence which introduce information or ideas that are new, or are not essential to an understanding of the rest of the sentence.
Dashes
Dashes tend to be used in more informal writing such as personal e-mails or blogs, and can often be seen in newspaper reporting. They are often, but not always, used in pairs.
Several hundred residents – like the couple in this photograph – have been left homeless by the floods.
Dashes can also introduce after-thoughts, particularly those that are surprising or unexpected:
Everyone turned up for the wedding – even Sally.
They tend to be more conversational, and it is hard to use them inaccurately. Just remember to use them sparingly when you are writing formally.