[If you would like this quote as a Word document to use as a teaching and learning support, here it is.]
“6. Do not break sentences in two.
In other words, do not use periods for commas.
I met them on a Cunard liner many years ago. Coming home from Liverpool to New York.
She was an interesting talker. A woman who had traveled all over the world and lived in half a dozen countries.
In both these examples, the first period should be replaced by a comma and the following word begun with a small letter.
It is permissible make an emphatic word or expression serve the purpose of a sentence and to punctuate it accordingly.
Again and again he called out. No reply.
The writer must, however, be certain that the emphasis is warranted, lest a clipped sentence seem merely a blunder in syntax or in punctuation. Generally speaking, the place for broken sentences is in dialogue, when a character happens to speak in clipped or fragmentary way….”
Excerpted from: Strunk, William Jr., and E.B. White. The Elements of Style, Fourth Edition. New York: Longman, 2000.