(Not a teacher)
Free morphemes are morphemes that can stand alone and still have semantic/functional meaning. They can be split into two categories:
- Lexical - nouns, verbs, adjectives (words that carry meaning and are the content of a message)
- Functional - conjunctions, prepositions, determiners, pronouns (words which have no semantic meaning as such, but perform a grammatical role)
Bound morphemes do not exist on their own and are attached to free morphemes (the are bound to them). They too can be split into two categories:
- Derivational - these give rise to new words, often changing the word class, for example: suffixes: -ish, -ness, -ly, -ment; prefixes: re-, pre-, ex-, dis-, co-, un-.
- Inflectional - these indicate aspects of grammatical function, for example: -ed, -s, -ing, -er, -est, -'s.
The bound morphemes are added to the free morpheme (also known as the 'stem') by two processes; affixation and modification. Affixation is the easiest to notice - it is simply the free morpheme with the affix attached. In English,
all inflectional morphemes are suffixes - car
s, walk
ing, talk
ed. Derivational morphemes can either be prefixes -
disappear; suffixes - shy
ness; or indeed both -
untime
ly.
Modification is more complex and applies to irregular forms. In most cases
part of the stem (most commonly the vowel) changes its sound structure when the morpheme is added. This is called
partial modification - man - men, catch - caught, go - gone. In English, there is only one example of
total modification, that is there are no features left of the original stem when the bound morpheme is added - go - went.
There are also some cases of a combination of affixation and modification - child - children (note the difference in vowel sound -the modification, although this is not represented in the spelling).
So, remember that words that have been modified by a bound morpheme contain two morphemes - the free morpheme + the bound morpheme. When we talk about morphemes, we name them according to their grammatical function. This is because, for example, the 'past morpheme' doesn't modify the stem the same way in each irregular past tense verb - caught, went, did all contain the past morpheme.
men = man + plural morpheme
caught = catch + past morpheme
children = child + plural morpheme (and remember the plural morpheme here is both affixed (-ren) and partially modified (the vowel sound)
went = go + past tense morpheme
I hope this clarifies your question.