Scientific English as a Foreign Language
Lesson of September 1, 1999
Adjective or Adverb?

"In Figure 4, the subdomains oriented perpendicular to the scan direction (more specifically, those with their tilt direction perpendicularly to the scan direction)...."

Do you recognize the two small mistakes in the phrase above? They concern perpendicular and perpendicularly, an adjective and an adverb, respectively. It isn't always easy to distinguish between an adjective and an adverb, and thus to use them correctly. Examples:

 I caught an early train. (Early is an adjective.)
 We finished early today. (Early is an adverb.)
 That was a kindly gesture. (Kindly is an adjective.)
 Would you kindly refrain from smoking? (Kindly is an adverb.)

One test to help determine if a word is an adjective is to try and use it in predacative form, that is:

 The train is early. (OK, adjective)
 Today is early...? (definitely not an adjective)
 The gesture was kindly. (OK, adjective)
 Smoking is kindly....? (Here there could be debate!)
Now we apply this test to the initial example.
 The tilt direction is perpendicular. (OK, adjective)
 The subdomains are perpendicular. (Hmm, perpendicular to what?)
 The subdomains are oriented perpendicularly. (much better, adverb)
The corrected version of the initial phrase is "In Figure 4, the subdomains oriented perpendicularly to the scan direction (more specifically, those with their tilt direction perpendicular to the scan direction)...."

There are four characteristics of an adjective.

The first is that an adjective can be used in a predicative form, "The train is early."
Second, it can perform an attributive function, as in "the early train..."
Third, it can be premodified by "very" -- "the very early train."
And the fourth characterisic is that adjectives can be made into comparitives and superlatives, e.g. "earlier" and "earliest".
Use these characteristics to help you determine if the word in question is an adverb or an adjective. Most adverbs take "ly" as a suffix.

Are the sentences below correct? If not, how should they be written?

 1. The derivation was easy debated. easily debated
 2. The easy derivation was debated. OK
 3. The slope of the second curve is steeper than the first one. OK
 4. The slope drops off more steep. steeply
 5. Preliminary results were previously published. OK
 6. Previous results were too preliminary. OK
We are grateful to Delphine Gourdon for the uncorrected initial example and to "A Student's Grammar of the English Language" by Greenbaum and Quirk (Longman Press, 1990) for clarifications and other examples.


Physics is like sex: sure, it may give some practical results, but that's not why we do it.

-attributed to Richard Feynman


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Created 1 September 1999, by Nancy Burnham and Fred Hutson.