SEMICOLONS TO JOIN INDEPENDENT CLAUSES (SENTENCES)
Use a semicolon to join very closely related sentences and make them into one sentence.
In an interview, hold your head up and don’t slouch; it is important to look alert.
Make good eye contact; looking down is not appropriate in an interview.
SEMICOLONS WHEN ITEMS IN A SERIES CONTAIN COMMAS
For more on using semicolons to join sentences, see “Coordination” in Chapter 17.
Use a semicolon to separate list items that themselves contain commas. Otherwise, it is difficult for readers to tell where one item ends and another begins.
I have a cousin who lives in Devon, England; another cousin who lives in Derry, New Hampshire; and a third cousin who lives in Freeport, Maine.