I believe a writer must know how to define simple, compound, and complex sentences before using them consciously. To me, that's so obvious it hardly needs stating.
Once a writer knows how to write a simple sentence, it is possible to apply strict mechanical "rules" for writing both compound and complex sentences. And with just these three sentence types, it is possible to write good essays, with good sentence variety, perfectly acceptable for academic work.
The explanations to the left are followed by "sentence identification" quizzes. Review the results between quizzes so you completely understand the use of coordinators and subordinators and punctuation in compound and complex sentences.
For information about online composition classes at this site, go to The ESLBEE.COM Academy.
The use of appositives is another excellent tool to introduce sentence variety. An appositive is a noun or noun phrase that immediately follows another noun. An appositive explains or defines the noun it follows and is set off by commas.
Below are two examples of appositives, the first sentence containing one appositive and the second sentence containing two appositives:
Each appositive in the examples above is set off by commas. Appositives are always set off by commas. Another interesting aspect of appositives is that they can always (or at least almost always) be exchanged with the nouns they modify as in the following example:
In the examples above, the appositives are in bold. In each case the appositive and its commas could be omitted from the sentence completely leaving excellent sentences as is shown.
When you understand the use and punctuation of appositives, go to the WRITING APPOSITIVES QUIZ. In this quiz, it is necessary to type sentences and add correct punctuation when required. Be sure to read the directions and type correctly. Spelling and punctuation count!
Finally, if you have not already done so, download the Transitions and Connectors Worksheet to help identify simple, compound, and complex sentences.