Sometimes you get a glimpse of a semicolon coming, a few lines farther on, and it is like climbing a steep path through woods and seeing a wooden bench just at a bend in the road ahead, a place where you can expect to sit for a moment, catching your breath.
Lewis Thomas, Notes on Punctuation,
The Medusa and the Snail 1979
The punctuation mark used to indicate a major division in a sentence where a more distinct separation is felt between clauses or items on a list than is indicated by a comma, as between two clauses of a compound sentence.
Use the semicolon to link independent clauses not joined by a coordinating conjunction. Semicolons should join only those independent clauses that are closely related in meaning.
Abdominal exercises help prevent back pain; proper posture is also important.
The auditors made six recommendations; however, only one has been adopted so far.
Do not use a semicolon to link a dependent clause or a phrase to an independent clause.
[WRONG] Although gaining and maintaining a high level of physical fitness takes a good deal of time; the effort pays off in the long run.
[RIGHT] Although gaining and maintaining a high level of physical fitness takes a good deal of time, the effort pays off in the long run.
Generally, you should not place a semicolon before a coordinating conjunction that links two independent clauses. The only exception to this guideline is if the two independent clauses are very long and already contain a number of commas.
[WRONG] The economy has been sluggish for four years now; but some signs of improvement are finally beginning to show.
[RIGHT] The economy has been sluggish for four years now, but some signs of improvement are finally beginning to show.
It may be useful to remember that, for the most part, you should use a semicolon only where you could also use a period.
There is one exception to this guideline. When punctuating a list or series of elements in which one or more of the elements contains an internal comma, you should use semicolons instead of commas to separate the elements from one another:
Henrys mother believes three things: that every situation, no matter how grim, will be happily resolved; that no one knows more about human nature than she; and that Henry, who is thirty-five years old, will never be able to do his own laundry.
HyperGrammar, Faculty of Arts, University of Ottawa
Put semicolons outside closing quotation marks.
Williams described the experiment as a definitive step forward; other scientists disagreed.
Owl On-Line Writing Lab
Semicolons with the word however:
Using however as a conjunctive adverb: However can be used to join
two simple sentences to make a compound sentence. However indicates the
relationship between the two independent clauses is one of contrast or opposition. Use a semicolon
before and a comma after however when you are using it to
write a compound sentence.
The engineers claimed that the bridge was safe; however, they were
still not prepared to risk crossing.
University of New England
For information about usage of the semicolon, click here to consult one of the many style books listed on the Resources page