Clarity and conciseness in writing is a beautiful thing. Sometimes we get so tangled up in what we are trying to say that we write monstrously long and convoluted phrases. Here's how to untangle a run-on sentence.
Determine whether the sentence is indeed a run-on. Suspect a run-on if the sentence contains more than 25 words and has multiple clauses: "Thales, who was the first Greek philosopher-scientist, developed geological and astronomical theories that have been outdated for thousands of years, and yet his wisdom endures, such as his timeless adage that the most difficult thing one can do is "to know oneself.'"
Isolate the verbs and conjunctions in the sentence. In our example, these would be developed, endures and and.
Delete the conjunctions and change verb tenses (if necessary) to form two or more sentences: "Thales, the first Greek philosopher-scientist, developed geological and astronomical theories that have been outdated for thousands of years. His wisdom endures, however, including his timeless adage that the most difficult thing is "to know oneself.'"
Add a transitional word or phrase if necessary to tie the sentences together. In the above case, the word however emphasizes the difference between Thales's outdated teachings and his wisdom.
Read the sentences aloud to make sure they are concise and clear. If you trip over any wording or phrases, you probably need to split up the sentences even more.
Tighten up your writing as you review it by deleting unnecessary words. Excessive use of the words which and that often accompany sloppy writing and runon sentences. Some of America's most acclaimed writers, including Walt Whitman and William Faulkner, have written whopper run-on sentences. Unless you are writing to achieve a certain literary effect, however, it is best to avoid run-ons.