Comparisons--similes, metaphors, and analogies--are invaluable tools to the writer of educational or instructional documentation. They convey a lot of descriptive information without a lot of dull words.

Compare the unknown to the known

       By comparing or contrasting something the reader is not familiar with to something he knows quite well--especially something he can visualize--you avoid considerable boring descriptive text.

If you were trying to explain to a child how long six feet is, you could say, "That's about as long as your daddy is tall." You would be using a comparison to make your meaning clear by using images your reader can grasp quickly.

The nice thing about analogies is that they put your reader at ease, let him know that this piece of learning is going to be easy, and sets up a cozy rapport between the two of you.

In non-technical literature, writers often employ two figures of speech that involve exaggerated comparisons: simile and metaphor.

Similes compare unlike things

       A simile is an expression that explicitly compares two unlike things, using like or as:

Metaphors make implied comparisons

       A metaphor implies a comparison by applying a term or phrase to something to which it is not literally applicable, such as: "The road was a silver ribbon."

Analogies work best in business writing

       In technical or business writing, however, the most useful form of comparison is the analogy, a form of reasoning in which two things are compared through known similarities--often comparing an unfamiliar thing to something familiar.

"Carbon filter elements look like solid or broken charcoal briquets, but seen under a microscope, the carbon granules look like sponges, with little canals and pockets that trap suspended solids." ¹

"No expression describes the typical comet better than "dirty snowball." Basically, that's what comets are--chunks of ice and frozen gases mixed with rocky debris. The snowballs range in size from 100 yards in diameter to 50 or 60 miles." ²

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¹ Cochran, Marian, 1985. Evaluation and recommendation of drinking water sources for residents of Spartan City. Formal report, San Jose State University.

² Rensberger, Boyce, 1986. How the world works. New York: William Morrow.