Compound sentences combine two clauses into one sentence. (Clauses are each a potential sentence with a subject and predicate.) Complex sentences do that too.
However, compound sentences use a conjunction (or sometimes a semicolon) to join two or more equal, independent clauses.
You could put the list above into simple sentences, each starting ‘The conjunction____.’
A shorter, more elegant, alternative is to combine facts about the most common conjunctions into one compound sentence:
The conjunction ‘and’ combines two similar thoughts; ‘but’ shows a contrast between the thoughts; ‘or’ indicates that only one of the two applies; and ‘so’ shows that the second thought follows from the first.
It’s also possible to combine two independent clauses without a conjunction between them by using a semicolon instead of a comma to separate them.
(That's what I did in the example in italics above. Only the last 'and' is used as a conjuntion there, so we need semicolons to combine the first three clauses. The final semicolon is to be consistent.)
You can say ‘I like ice cream, but he prefers butter.’ You can also say ‘I like ice cream; he prefers butter.’ Both are correct, although sometimes using a conjunction makes the thought clearer.
You can express the connection between ideas using two sentences rather than one compound sentence. Instead of using ‘and’ between clauses, you could make the second clause a new sentence beginning ‘in addition’ or 'furthermore.'
Contrasting sentences can begin with ‘however’ or ‘nevertheless;’ others with ‘as a result,’ ‘consequently,’ ‘as an alternative,’ ‘instead,’ etc.
However, these are all more formal than a compound sentence. (I thought about demonstrating these with the same example of family trips to the zoo, but we would never use such academic language for a family trip!
I can’t imagine one parent telling another, “Larry’s family went to the zoo. However, they didn’t enjoy it.” In conversation English speakers would use ‘but’ every time!)
Sometimes two sentences can be combined without needing to
make a compound sentence. If both
subjects or both verbs are the same, two sentences can be joined into one
simple sentence (= only one clause) with a compound subject or a compound verb.
Note that in the last example I changed the form of the 2nd verb (from a present participle to an infinitive) so they would share the same form. Parallel constructions are easier to understand and sound better. Teachers and test-givers look for them when reading essays. (They may take off points when two similar thoughts are expressed in different ways:
Michael rides his bike every day. He also practices judo and is always watching baseball games on T.V.)
Michael rides his bike every day. He also practices judo and watches baseball games on T.V.
or: Michael rides his bike, practices judo, and watches baseball games on T.V. every day.
Take out a piece of paper and combine these sentences.
You can make compound sentences, using a comma and conjunction or a semicolon (;), or sometimes you can make a simple sentence using a compound subject or verb.
Use parallel constructions whenever possible. (Answers at the bottom of this page.)
1. I have studied Spanish for many years. As a result, my Spanish-speaking friends can chat easily with me now.
2. You are quite intelligent. However, you don’t think before you act.
3. My friends Jesse and Jennifer have just moved into a new home. They’ve made many changes in its appearance.
4. Susie could study music next year. She could study drama instead.
5. Larry watches the news.Bill makes news.
Compound sentences are fairly easy to make, as they combine two similar clauses. Sometimes we need to combine unequal thoughts or clauses.
See English Sentence Structure for the basics of sentence formation.
Complex Sentences explains making sentences combining unequal clauses. It talks about noun, adjective, and adverb clauses, as well as subordinate conjunctions and relative pronouns,
1. I have studied Spanish for many years, so my Spanish-speaking friends can chat easily with me now.
2. You are quite intelligent, but you don’t think before you act.
3. My friends Jesse and Jennifer have just moved into a new home, and they’ve made many changes in its appearance.
or: My friends Jesse and Jennifer have just moved into a new home and made many changes in its appearance.
4. Susie could study music or drama next year.
or: Susie could study music next year, or she could study drama (instead). (You can omit ‘instead,’ or leave it in the sentence for greater emphasis.)
5. Larry watches the news, but Bill makes news.
or: Larry watches the news; Bill makes news.
(If I said these aloud, I would heavily stress ‘makes.’)