Semicolon

Use a semicolon:

• to separate two clauses not joined by a conjunction (and, but, or, nor, for, so, yet).

Air traffic delays due to high traffic volume have increased considerably over the last decade; these delays have become a major public policy issue.

• between independent clauses connected by a conjunctive adverb (however, nevertheless, moreover, then, consequently, also) or a sentence modifier (in fact, for example, on the other hand, in the first place).

Existentialism is chiefly a twentieth-century philosophy; in fact, it received its impetus from the despair following World War II.
Increasing the size of airports is one solution to traffic congestion; however, this is a long-term solution whose benefits may not be seen for many years into the future.

• the semicolon is a stronger type of punctuation than commas and can also be used to to separate rather long items in a list or to separate items in a series already punctuated with commas.

The television interview focused on three guests: a professor form the University of Surrey, well-known for his stand against the neutron bomb; a member of Greenpeace, passionately devoted to environmental affairs; and an MP from Dalkeith, Scotland.