3a. A colon appears at the end of a main clause. Because
of this rule, you can ask yourself this question: "Considering
the wording before this point, could I put a period or question
mark here?" If the answer is yes, then you may use a colon to
attach the following material to the sentence as long as that material
is a list, a restatement, or an elaboration.
This rule also means that you should not use a colon to introduce
a list which completes the kernel of a main clause.
Unable to ascertain the exact cause of death, the doctor
turned the body over to a team of forensic experts: Janice
Trico, the county coroner; Gerald Sota, the county sheriff; and
Michael Jesperson, the head of the county crime lab.
3d. A colon introduces an elaboration of the main clause.
I've decided not to take the assistantship for next year: The Prudential
company has made me an offer I can't turn down.
wrong: On our farm, we grow: wheat, alfalfa, and
soybeans.
3b. A colon introduces a list. It is important to remember
that a colon introduces a list only when the list is attached to
a completed main clause.
okay: On our farm we grow three crops: wheat,
alfalfa, and soybeans.
We sent copies to our regional offices: the north-central
office in Traverse City, the south-east office in Tampa, and the
south-west office in Santa Fe.
3c. A colon introduces a restatement of the main clause.
No matter how often she turned it over in her mind, Carol
couldn't decide who was to blame: She couldn't decide whether to
blame herself or Jim.
Notice that the second main clause says the same basic thing as the
first. It is often hard to distinguish between a restantement and an
elaboration because any time you say something a little differently,
you tend to add new information; that is, you elaborate a little.
Also notice that the second main clause is capitalized. Different
style guides recommend different practices: Some suggest a capital;
others suggest lower case. Check the handbook you are using in class,
or ask your teacher for her or his preference. Try to be consistent.
Different style guides recommend different practices: Some suggest a capital;
others suggest lower case.
3e. A colon introduces a long quote, which is often indented.
Jeremy Rifkin has argued that Darwin built his theory on the analogy between
economics and nature:
It was Darwin who was ultimately responsible for formalizing the analogy
between economics and biology; and in so doing, says sociologist Robert
Young, he gave "the mark of scientific respectability to the equation
of the division of labor with the laws of life." Algeny, page 87.