1. 2. Sentence and Clause Combining
Forming Compound, Complex, and Compound-Complex Sentences

2. Terminology
In the previous lesson we spoke of adjective and adverb clauses. Adjective and adverb clauses can both be referred to as dependent clauses. From this class forward, for the sake of simplicity, we will use the broader term dependent clauses when making a point that applies to both adjective and adverb clauses.

3. Compound Sentences
A compound sentence is two independent clauses joined by a comma and a coordinator.
The coordinators are as follows: and, but, or, nor, for, yet, so
An alternative to joining independent clauses with a comma and a coordinator is to join them with a semicolon.
Example with comma and coordinator:
Our samples have arrived, so we can start.
Example with semicolon:
Our samples have arrived; we can start.

4. Punctuation point
A semicolon is equal in “strength” to a comma and a coordinator together.
A semicolon can also be used instead of a period. It should not be overused, however. Reserve it for occasions when the thoughts expressed in two independent clauses are very closely related.
She is a good professor. I admire people who are good at their jobs.
She is a good professor; her students succeed.
When you do use a semicolon, consider adding a logical connector (e.g. however, therefore) to clarify what the relation is.
She is a good professor; therefore, her students succeed.

5. Complex Sentences
Complex sentences are made up of one independent clause and one or more dependent clauses.
Complex sentence with one dependent clause:
After the fire, the lab could no longer be used.
Complex sentence with two dependent clauses:
After the fire, the lab where the scientists worked could no longer be used.

6. Subordinators
A dependent clause always begins with a subordinator. Subordinators can show such relationships as the following:
Time: when, before, after, until, whenever, since.
Cause/effect: because, so that, since
Compare/contrast: although, even though, even if, while, whereas
Possibility: if, as if, whether, unless
Place/manner: wherever, where, how

7. Punctuation point
In any combination of an independent clause and an adverb clause, the punctuation depends on the order of the clauses.
If the adverb clause comes first, a comma between the clauses is necessary.
Example:
Because they viewed the method as unsound, they rejected the article.
No comma is necessary if the adverb clause follows the independent clause.
They rejected the article because they viewed the method as unsound.

8. Compound-Complex Sentences
A compound-complex sentence is made up of two independent clauses (IC) and one or more dependent clauses (DC).
Example:
Although I like to go camping (DC), I haven’t had time lately (IC), and I haven’t found anyone to go with (IC).

9. Caution
Note that joining independent clauses without a comma and a coordinator (or a semicolon) is ungrammatical.
Example:
This is a valuable new study, it addresses unresolved problems in the field.
The most obvious solution in this case is simply to add the missing element: a comma and a coordinator or, as below, a semicolon.
This is a valuable new study; it addresses unresolved problems in the field.