There are several types of introductory elements to
First, there are introductory clauses.
These dependent clauses provide background
information or "set the stage" for the main part of
the sentence, the independent clause. Usually,
these clauses start with adverbs like after,
although, because, before,
if, since, though, until,
Although the safest automobile on the road is
expensive, the protection it offers makes the
Second, there are introductory phrases.
Unlike introductory clauses, these phrases do not have a subject
and a verb that are separate from the subject and
verb in the main clause of the sentence. Common
introductory phrases include prepositional
phrases (phrases that begin with words such as of, to, at,
in, of), adverbial phrases
like Once upon a time, and participial
phrases like working around the clock.
In December two snow storms delayed our trip
to the mountains.
Third, there are singular words such as interjections
(e.g., oh, yes, no, why) and
conjunctive adverbs (e.g., however, still,
However, you do need to vacuum the upstairs
********Did you notice
that the second example sentence did not have a
The explanation is
general, you do need a comma after introductory
elements in the following cases:
introductory phrases (Ask yourself, “are there
more than five words before the main clause?”)
do not need a comma if there is a short
introductory prepositional phrase (Ask yourself,
“is it a single phrase of less than five
words?”). A better way to put this might
be to say that the comma is optional. You
should include a comma if there is a potential for
the reader to misunderstand or misread the sentence.
Let's consider this sentence: "During the winter,
vacation plans for the summer are all I can think
about." In this case, if the writer omitted
the comma, we might initially think that winter is
an adjective modifying vacation. It's not, of
course. It's a noun describing time of year. The
comma emphasizes that winter functions as a noun as
part of the introductory prepositional phrase and
not as an adjective modifying "vacation."
*One Note of Caution*: It is very important to
identify the difference between the subject of the
sentence and an introduction.
For example, in the
sentence, “Studying all weekend, I felt very
prepared to take the test,” studying all weekend
is an introductory phrase, for I is the subject of the sentence (the independent
clause). Now, in this sentence, “Studying all
weekend prepared me to take the test,” studying
is not an introductory phrase but the subject of the
sentence, for there is no other independent clause.
Therefore, a comma is not needed because you would
be separating the subject from the predicate.
Mond is a peer writing tutor at the University of
Houston-Victoria and an education major. She began working
in the Academic Center in spring 2008 and is CRLA certified
at level 2. She enjoys spending time with her friends,
family, and her silly miniature schnauzer Dixie.
Benner, M. L.
(2008). Comma. Towson University’s Online Writing Support.
Retrieved March 11, 2009, from
Commas after introduction (2004). Purdue University Online
Writing Lab. Retrieved March 11, 2009, from
Glenn, C. & Gray, L. Hodges’ Harbrace Handbook (16th Ed.)