Commas, Semi-colons and Colons

Demarcating Sentences

This refers to the beginning and ending of sentences.

Sentences should always start with a capital letter and end with either a full stop, question mark or exclamation mark.


There are 4 main reasons for using a comma in a sentence:

  • To separate main clauses from subordinate clauses.
  • To separate connectives from the rest of the sentence.
  • To add extra information in parenthesis.
  • To separate items in a list (the comma does not precede the “and”).


Problems occur with incorrect use of commas, in particular comma splicing. This is when two independent clauses are linked by a comma – which is grammatically incorrect.

The steam train roared through the station, great clouds of smoke and steam billowing from its funnel, it was terrific!

“It was terrific!” is an independent clause – it makes sense on its own so should not be comma spliced.

The steam train roared through the station, great clouds of smoke and steam billowing from its funnel.
It was terrific!

 Colons and Semi-Colons

Colons :

Colons are used before a list.

For lunch she ate: sandwiches, crisps, grapes and strawberries.

You don’t put a comma before the and.

Colons are also used in a glossary.

adjective: describes a noun
adverb: describes a verb

Semi-colons ;

Semi-colons are used to separate items in a list when the items are longer than one or two words.

Day-trips to the Brecon Beacons could include: walking up Pen Y Fan; cycling along the Taff Trail; visiting the mountain centre and exploring the shops in Brecon.

Semi-colons can also be used to join two closely related clauses in sentences, or to take the place of connectives.

Ian ate the whole meal but Amy just ate dessert.

Ian ate the whole meal; Amy just ate dessert.
It was a sunny day so the children applied sunscreen.

It was a sunny day; the children applied sunscreen.

Colons and semi-colons together

Colons and semi-colons are used together in bulleted lists, but only when the bullet points are a number of words.

Wales is a great place to go on holiday because:

  • There is some spectacular scenery;
  • Cardiff has great shops;
  • You can try amazing food in the restaurants and cafes.


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