The power of parallelism

Here is an easy way to add strength to you writing. Your readers will bless you for it, because it makes it easier on them.

Parallel construction, in the words of William Strunk, "requires that expressions of similar content and function should be outwardly similar. The likeness of form enables the reader to recognize more readily the likeness of content and function."

Wrong: Formerly, science was taught by the textbook method, while now the laboratory method is employed.
Right: Formerly, science was taught by the textbook method; now it is taught by the laboratory method.

Strunk: "The first version gives the impression that the writer is undecided or timid; he seems unable or afraid to choose one form of expression and hold to it. The second version shows that the writer has at least made his choice and abided by it."

By this principle, an article or a preposition applying to all the members of a series must either be used only before the first term or else be repeated before each term.

Wrong: In spring, summer, or in winter
Right: In spring, summer, or winter (In spring, in summer, or in winter)

Red flags: Correlative expressions (both, and; not, but; not only, but also; either, or; first, second, third; and the like) should be followed by the same grammatical construction.

Wrong: It was both a long ceremony and very tedious.
Right: The ceremony was both long and tedious.