Examples and Observations:
- "There are two basic types of morphemes: unbound and bound. Unbound or free-standing morphemes are individual elements that can stand alone within a sentence, such as <cat>, <laugh>, <look>, and <box>. They are essentially what most of us call words. Bound morphemes are meaning-bearing units of language, such as prefixes and suffixes, that are attached to unbound morphemes. They cannot stand alone.
"Their attachment modifies the unbound morphemes in such things as number or syntactic category. Adding the bound morpheme <s> to the unbound morpheme <cat> changes the noun's number; the addition of the <ed> to <laugh> changes tense. Similarly, the addition of <er> to <run> changes the verb to a noun."
(Stephen Kucer and Cecilia Silva, Teaching the Dimensions of Literacy. Routledge, 2006)
- "Linguistics recognizes two classes of bound morphemes. The first class is called inflectional morphemes and their influence on a base word is predictable. Inflectional morphemes modify the grammatical class of words by signaling a change in number, person, gender, tense, and so on, but they do not shift the base form into another word class. When 'house' becomes 'houses,' it is still a noun even though you have added the plural morpheme 's.' . . .
"Derivational morphemes constitute the second class of morphemes and they modify a word according to its lexical and grammatical class. They result in more profound changes on base words. The word 'style' is a noun, but if I make it 'stylish,' then it is an adjective. In English, derivational morphemes include suffixes (e.g., 'ish,' 'ous,' 'er,' 'y,' 'ate,' and 'able') and prefixes (e.g., 'un,' 'im,' 're,' and 'ex')."
(Donald G. Ellis, From Language to Communication. Lawrence Erlbaum, 1999)