A sentence is a basic concept: it includes a subject, a verb and a complete thought. Simple stuff.
A sentence can be very simple: “John ran.” Or, it can be very complex: “John ran to the store when he finished working in the yard because he was thirsty and needed something to drink.”
The first sentence has a subject, “John,” a verb, “ran,” and is a complete thought: What did John do today? John ran. Sure you might want to add more info to make the thought easier to comprehend, but it’s still a complete thought. “When John ran,” would be considered an incomplete thought because we need more information.
The second sentence has the same verb structure: “John ran,” but it includes a whole lot more- “he finished” is a subject/verb; “he was thirsty and needed” is another. But only “he ran” is the main idea of this sentence. Main ideas are the parts of the sentence that can stand alone. As we already said, “John ran” can be a sentence by itself. But “when he was finished” is an incomplete thought, as is “because he was thirsty.”
Sentences that can stand by themselves are considered “coordinating structures.” That means they are main ideas that do not need more information to be grammatically correct. “I ran to the store, and I bought a six-pack of Pepsi,” has two main ideas. The connecting words (and, but, so, for, or, nor, and yet) connect main ideas in a sentence. You never want to have more than two main ideas in a sentence: “John went to the store, and he bought a six-pack, so he was happy.”
Other parts of the sentence that add additional information but cannot stand by themselves are called “subordinate structures.” This means they would be fragments if left to themselves. “When John went to the store, he bought some soda.” Now, “he bought some soda” has become the main idea while “When John went to the store” is less important or subordinate. This is a good tool for emphasizing one idea over another in a sentence.
I’d like to break sentences into three categories, loose, periodic and balanced:
- Loose sentences begin with the main idea: “Gary and Susan drove to Portland for their vacation.” Gary and Susan is the subject, drove is the verb. They are placed at the beginning of the sentence. “Tom waited for the rain to stop before heading out into the woods.” This begins with the subject verb and then adds some additional information. It is important that most of your sentences begin with subject/verb structures. They are the most important part of the sentence and push the reader into the rest of the sentence.
- Periodic sentences begin with less important information and lead up to the main idea (subject/verb). “When Gary and Susan drove to Portland, they decided to stay at Ramada Inn.” Gary and Susan is still a subject in the sentence, but with the word “when” attached, it becomes subordinate. The main idea of the sentence now becomes “they decided…” Periodicy slows reading down. Readers are looking for main ideas, and when they are buried in the middle of the sentence, it is harder to find them. Use periodicy sparingly, one or two times per paragraph at the most.
- Balanced sentences have two main ideas: “Gary wanted to go to Portland, but Susan thought Bangor would be better.” This has two main ideas connected with one of those seven words listed earlier that identify main ideas. You don’t want to have too many balanced sentences, because main ideas will battle one another for superiority in a sentence, and your reader will become confused.
Of course there is a lot more to know about sentences than this. Your grammar book has some detailed information on how to write effective sentences. Check specifically sections 19 and 20 for some more information on what I’ve just summarized. I also have a practices for you in the Written Assignment area to practice.