By Sherri Byrd
English Grammar:  ENG 371
Student of
Dr. Mark Canada
University of North Carolina at Pembroke, 1998

    To classify words, grammarians use two large categories called form and functionFunction is how the word or the phrase is used within the sentence or clause, while form classifies the word or phrase by a simple definition along with some general rules.  For example, a noun is classified in form as a word that can made be plural or possessive.  The following sentence gives an example of the difference between the two categories:
                We admired the stone wall.   In this sentence "stone" in function is an adjectival that modifies "wall."  In form "stone" is a noun because it can be made plural or possessive:  "stones" and "stone's."
This can be better understood in a Web site titled  "Adverbials."  We can change the class of a word by adding prefixes or suffixes.  Example:  The word "play" is a verb, but it can be changed to an adjective by adding -ful to make it "playful."  The girls play.  The girls are playfulTherefore, the class of the word has changed from a verb to an adjective.

There are four form classes:

Here are some characteristics of the different form classes that will help you distinguish between them: All of these form classes have derivational and inflectional affixes.  These affixes are prefixes or suffixes that change the meaning or the class of a word.  Example:  Adding in- or un- to a word can make the word negative.  She is happy.  She is unhappyThe first sentence means that she is happy, and the second one means that she is not happy.  An affix may not work for every word in a class, however. Example: Adding -ful to a verb can make it an adjective, but this is not true for all verbs.  You could make "thank" into "thankful," but you could not use this suffix in the verb "talk" to make it "talkful."  You would add a different suffix: "talkative."  The only explanation that can be given for these inconsistencies is that these are rules in the English language that deal with the morphology of word and how they are used.  It is something that can be chased back for centuries.  This is why it is always useful to have a dictionary if you ever have any questions about a word and its different classes. 
Form Class
Derivational Affixes
-ion*, -ment, -ance
-s*, -'s*,-s'*,
en-, be-, de-, -ify, -en, -ate, -ize
-s*, -ing*, -ed*,-en*
-ous*, -y, -ful, -fic, -ic, -ate, -ish, -ary, -ive, -able
-er*, -est*
-ly*,-wise, -ward
-er*, -est*
*These affixes very often can help you determine the class of the word.  For example, most words that end in "-ly" are adverbs.

These are only a few examples of affixes that can be used to change words to other classes.  To learn more about some affixes and their meanings, go to a site titled Morphemes.


  • The Form Classes classify most of the words in the English Language.
  • All of the classes have derivational affixes, which can change the class of one word to another class.
  • Remember, if you ever wonder in what situation a word should be used or what the correct affix for a word is, you can refer to a dictionary. 
  • Knowing the affixes of the classes can help you improve your lexicon (vocabulary) to make it more varied.  Your writing can also improve because it will help you flow from one class to another easily.

  • Example:  If you know that you can make a noun from a verb by adding -ion( act--action), then that is another way to use that word and you have another word in your "mental dictionary."

I.    Change the form of these words by adding the correct derivational affixes.
             Noun              Verb           Adjective          Adverb
    1.                                    act
    2.        form
    3.                                     teach
    4.                                                                partial 

    5.                                                                                                beautifully
II.   Use Inflectional suffixes to make the sentences grammatically correct.
    1.  The school was work hard for donations.
    2.  The boy paper was written on the computer. 
     3.  That ladder is the high among the three.

     4.  This picture is the pretty of the two.

     5.   All of the dog bones were put in their bowls for their dinner.

Click here for answers to these exercises.

 Kolln, Martha and Robert Funk.  Understanding English Grammar.  5th ed.  Boston:  Allyn & Bacon, 1998.

Fromkin, Victoria, and Robert Rodman.  An Introduction to Language.  Fifth Edition. Fort Worth:  Harcourt Brace Jovanovich College Publishers.  1993.