Semicolons before conjunctions

The Quick Answer
When a conjunction (words like and, but and or) is used to merge two independent clauses into one sentence, it is possible to use a semicolon before the conjunction to outrank any commas in the clause. (This practice is acceptable, but it is considered outdated these days. However, if you think a semicolon makes your sentence clearer, you can use one.)

Semicolon before a Conjunction

When a sentence made up of two independent clauses contains commas, it is possible to use a semicolon before a conjunction which joins the two independent clauses to outrank any commas in those clauses.

Examples:
  • In fact, rather surprisingly, the majestic pike is hardly used in cooking today; but in Victorian times, pastry-topped pike was a very common dish.
  • (Semicolon used before but to outrank the other commas in the sentence.)

semicolon used before but to outrank the other commas (correct usage)
(magazine article)
  • As the Dutch captain drafted the order banning the killing of the dodos, his sailors had the last one in their sights; and, as the muskets sounded, dodos were gone forever.
  • (semicolon before and)
  • Shakespeare, a great dramatist, wrote a great many plays; and he wrote a number of sonnets too.
  • Before a war, military science seems a real science, like astronomy; but, after a war, it seems more like astrology. (Rebecca West, 1892-1983)

See Also

What are conjunctions? Run-on error with a comma Conjunctions and commas Conjunctions and semicolons Using semicolons before transitional phrases (e.g. however) Using semicolons in lists Using semicolons to extend a sentence