The Semicolon ( ; )

The semicolon is used to separate independent clauses, and to separate items in a list. Whereas the colon moves the reader forward providing an elaboration of what went before (in the form of an example or definition), the semicolon only acts as a separator.

Semicolon separating independent clauses

• Most foods contain at least some sugar; once foods are between 230 and 320 degrees, their sugars begin to turn brown
• For instance, our Milky Way galaxy has at least 100 billion stars; that means it has at least 100 billion planets too .
• The best-performing chimpanzees remembered at least four items; one young chimpanzee remembered more than seven .
  
  A sentence containing independent clauses not separated by a semicolon is known as a run-on sentence.

Semicolon for separating items in a list

We already have commas for separating items in a list, so why do we need to use the semicolon? The reason is that sometimes the items in the list are long and may themselves contain commas. It this case we need another separator to avoid confusion.

• Our Earth is structured sort of like an onion – it’s one layer after another. Starting from the top down, there’s the crust, which includes the surface you walk on; then farther down, the mantle, mostly solid rock; then even deeper, the outer core, made of liquid iron; and finally, the inner core, made of solid iron, and with a radius that’s 70% the size of the Moon’s .
• The evaluation process for a classification includes: medical, visual or cognitive testing; demonstration of sport skills; and observation during competition .

Test your understanding of semicolon punctuation with the Colon/Semicolon Punctuation Quiz.