Semicolons before conjunctions
 
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 (This practice is acceptable, but it is considered outdated these days.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 indepedent 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)
 
IT'S OLD FASHIONED

Many people consider it old fashioned to use a semicolon before a conjunction these days.
 
 
CO-ORDINATE CONJUNCTION

Words like and, but and or are called conjunctions. Sometimes (as in the examples below), they join two sentences together to form one. When conjunctions are used in this way, they should be preceded by a comma. In this role, they are called co-ordinate conjunctions.

  • She cannot abide tennis, but she loves watching golf.
  • (Sentence 1: She cannot abide tennis.
    Sentence 2: She loves watching golf.)
    (but merges the two sentences – co-ordinate conjunction – comma required)
  • I may consider your plan, or I may stick with mine.
  • (or – co-ordinate conjunction – comma required)
So, when a conjunction joins two standalone sentences (or independent clauses), it will be preceded by a comma. This page is about upgrading that comma to a semicolon to outrank any commas within those clauses.

Note: The word co-ordinate just means of equal rank. In these sentences, both halves are considered to be the same rank (i.e., they are both full sentences).
 



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



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