Adjectives describe, modify, or limit the meaning of nouns. 
They tell what kind: a red barn, a swift ride, a happy woman. 
Adverbs describe, modify, or limit the meaning of verbs,
adjectives, or other adverbs.  They tell how, how much.


     The horse ran swiftly.  (swiftly modifies the verb; it tells
                              how the horse ran.)

     It was a very swift horse.  (very modifies the adjective; it
                                   tells how swift the horse was)

     It ran very swiftly.  (very modifies the adverb; it tells how
                              swiftly the horse ran)


     Many adverbs are formed by adding the suffix -ly to an
adjective: smoothly, quickly. But remember that not all words
ending in -ly are adverbs (exceptions include: friendly, saintly,
womanly).


1.   Use an adverb, not an adjective to:

          a. modify a verb:

               Wrong: He sure works hard.

               Right: He surely works hard.

          b. modify an adjective:

               Wrong: He was injured bad.

               Right: He was badly injured.

          c. modify an adverb:

               Wrong: I drive considerable faster.

               Right: I drive considerably faster.



2.   Use an adjective after a linking verb if the word modifies the
subject:

          Janet is jubilant. (jubilant modifies Janet)

          She looks happy. (happy modifies she)

          The flowers smell fragrant. (fragrant modifies flowers)

          He looked suspicious. (suspicious modifies he)


     If the modifier describes the verb, use an adverb:

          He looked suspiciously at the box. (suspiciously modifies
                                             looked)

[linking verbs include:  am, is, are, was, were, look, sound,
smell, feel, seem, appear, become, grow, remain]


3.   Some confusing forms.  People often confuse the adjectives
good and bad with the adverbs well and badly:

          Wrong:    The car runs good. 

          Right:    The car runs well. (well is how the car runs)

          Wrong:    My arm hurts bad. 

          Right:    My arm hurts badly. (badly is how much my arm
                                        hurts)

          Right:    I feel good. (good describes I; it is an
                                   adjective following the linking
                                   verb feel. Good here means
                                   happy.)

          Right:    I feel well. (well describes feel. it is an
                                   adverb describing how I feel. 
                                   Well here means healthy.)

          Right:    I feel bad. (bad describes I; it is an
                                   adjective following the linking
                                   verb feel. Bad here means
                                   unhappy.)