A complete sentence is not formed simply by starting a sequence of words with a capital letter and ending it with a period. Sentences additionally require a subject, a verb, and they must form a complete thought. Examples of incomplete sentences include:
I have so many fond memories of my favourite pastime. Happy days playing and enjoying golf.
There are far too many people travelling on public transport. Which is one reason why this terrible virus is spreading so quickly.
Until we can flatten the curve. This pandemic will overrun our health service.
Two ways to fix incomplete sentences are:
We can fix the examples above as follows:
I have so many fond memories of my favourite pastime. These were happy days playing and enjoying golf.
There are far too many people travelling on public transport which is one reason why this terrible virus is spreading so quickly.
Until we can flatten the curve, this pandemic will overrun our health service.
A common cause of sentence fragments is when a writer adds more information or clarifies the previous sentence. For example,
England has many towns and cities that date back to Roman times. Including York, Colchester, and St. Albans.
This example can be corrected like this:
England has many towns and cities that date back to Roman times, including York, Colchester, and St. Albans.
Or like this:
England has many towns and cities that date back to Roman times. These include York, Colchester, and St. Albans.
Look out for sentences starting with Including. These often start a sentence fragment.
Sometimes, when writing informally, incomplete sentences can be used. For example, when emailing friends, you might finish your message of with something like this:
See you soon.