When you write, you enter a contract with your reader. The first clause in your contract is that you make sense.

This clause applies to all of us, with the exception of candidates for political office. Poets, novelists, memoirists and comedians are also permitted some leeway here. As are newspaper columnists. But most of us, most of the time, are expected to be clear when we write or speak.

The second clause in your contract, which relates to the "clarity clause," is that you be consistent. You may not have noticed this clause, but take a look at your contract. It's right there in black and white. There's even a fancy name for it: parallelism, sometimes referred to as parallel structure or parallel construction. Different names, same idea.

Here's how it works.

When you create or "construct" a series of words or clauses, whether in a vertical list in a PowerPoint presentation or in a horizontal format like the words in this sentence, you're under contract to pre­sent the entire series in like fashion. Your reader expects consistency. Break the pattern and you jar your reader. My favorite example: "She was healthy, wealthy and an athlete." According to your contract, a series of two adjective requires a third adjective, not a noun, so to maintain parallel structure it should be "She was healthy, wealthy and athletic."

The "consistency clause" of parallel structure requires you to maintain the same pattern throughout a series of words or phrases.

A sentence like the following will jar your reader: "He was wise, judicious and tried to avoid offending people with thoughtless, undiplomatic comments." If you begin your series with adjectives, you must stay with adjectives, not shift to a verb phrase. Revised to maintain parallel structure, that sentence might read, "He was wise, judicious and circumspect."

Another way to correct a break in parallel structure is to divide the nonparallel series into two parts, as in "He was wise and judicious, and he tried to avoid offending people with thoughtless, undiplomatic comments." Here the series in the first part of the sentence has only two elements, both parallel, and the writer is free to trot off in any direction with a new structure that doesn't match the series, much as political candidates are free to say anything they like to get elected. Try it. It works.

Errors in maintaining parallel structure are especially apparent in vertical lists, both numbered and bulleted, whether in tables, charts or PowerPoint presentations. To find examples of nonparallel structure in these formats, you need only google "PowerPoint presentations."

As you read the advice, much of it excellent, you'll find lists mixing fragments and complete sentences like the following, which comes under the heading, "Avoid the Most Common Presentation Problems":

Lack of preparation or passion.

Slides are too complex, overloaded with bullets, lacking in focus and/or filled with poor quality images.

And this list: "Simplify, Lose the clichés, Information needs emphasis, Designate elements, Empathy for the audience."

Oh, my. Maybe this guy has a career in politics.

Stephen Wilbers offers training seminars in effective business writing. E-mail him at wilbe004@umn.edu. His website is www.wilbers.com.