Two sentences or parts of sentences that express equally important ideas
can often be combined into one sentence.
Combining to Show Addition
Ideas that are similar and equally important can be joined with the coordinating conjunction and.
Punctuation Note - When you join independent clauses into a compound sentence, place a comma before the coordinating conjunction.
When you combine sentences, delete any repeated information.
Punctuation Note - When you join two predicates no comma precedes the conjunction.
Such sentences may also be joined by a semicolon.
Sentences that have equally important ideas can also be combined using a conjunctive adverb (also, furthermore, likewise, moreover)
Punctuation Note - When two sentences are joined with a conjunctive adverb, a semicolon comes before the conjunction and a comma follows it.
- The world's largest steamship struck an iceberg shortly before midnight on April 14, 1912. It sank in less than three hours.
- The world's largest steamship struck an iceberg shortly before midnight on April 14, 1912, and it sank in less than three hours.
Punctuation Note - When you join independent clauses into a compound sentence, place a comma before the coordinating conjunction.
When you combine sentences, delete any repeated information.
- Ancient people built a circular structure at Stonehenge. These people used it to keep track of the sun's progress.
- Ancient people built a circular structure at Stonehenge and used it to keep track of the sun's progress.
Punctuation Note - When you join two predicates no comma precedes the conjunction.
Such sentences may also be joined by a semicolon.
- Rachel Carson took a required undergraduate course in biology. She went on to get a master's degree in genetics.
- Rachel Carson took a required undergraduate course in biology; she went on to get a master's degree in genetics.
Sentences that have equally important ideas can also be combined using a conjunctive adverb (also, furthermore, likewise, moreover)
- Rachel Carson took a required undergraduate course in biology; furthermore, she went on to get a master's degree in genetics.
Punctuation Note - When two sentences are joined with a conjunctive adverb, a semicolon comes before the conjunction and a comma follows it.
Combining to Show Contrast
Contrasting ideas of equal importance can usually be joined by the coordinating conjunction, but.
Contrasting ideas of equal importance can also be joined with the conjunctive adverb, however.
- Hong Kong had been a British Colony. China took over in 1997.
- Hong Kong had been a British Colony, but China took over in 1997.
- The explorer Henry Hudson was looking for a short route to Asia. He discovered the New York river that now bears his name.
- The explorer Henry Hudson was looking for a short route to Asia but discovered the New York river that now bears his name.
Contrasting ideas of equal importance can also be joined with the conjunctive adverb, however.
- The explorer Henry Hudson was looking for a short route to Asia; however, he discovered the New York river that now bears his name.
Combining to Show Choice
A choice between two ideas of equal importance can usually be expressed by using the coordinating conjunction, or.
- Was William Shakespeare's genius recognized during his lifetime? Was he viewed only as a popular entertainer?
- Was William Shakespeare's genius recognized during his lifetime, or was he viewed only as a popular entertainer?
- Experts believe that the 1936 explosion of a German airship was caused by lightning. It may have been caused by the carelessness of the crew.
- Experts believe that the 1936 explosion of a German airship was caused by lightning or by the carelessness of the crew. (Two prepositional phrases are combined.)