Chapter 12.2: Types of Morphemes

There are two primary types of morphemes: free morphemes and bound morphemes.

Free Morphemes

A free morpheme can carry semantic meaning on its own and does
not require a prefix or suffix to give it meaning. In other words, it can stand
on its own as a word, like the, boy, run, and
luck. Each of these morphemes can function independently.

Bound Morphemes

Bound morphemes cannot stand alone but must be bound to other
morphemes, like –s, un-, and –y.

Bound morphemes are often affixes. This is a general term that
comprises prefixes, which are added to the beginnings of words,
like re– and un-, and
suffixes, which are added to the ends of words, like –s,
–ly, and –ness. Some languages also have infixes,
which are added into the middle of words, but these are rare in Modern English.

Bound morphemes are further divided into two subtypes: derivational and
inflectional morphemes.

Derivational morphemes change the meaning or the part of speech
of a word (i.e., they are morphemes by which we “derive” a new word). Examples are
un-, which gives a negative meaning to the word it is added to,
–y, which turns nouns into adjectives, or –ness, which
turns adjectives into nouns.

Inflectional morphemes add grammatical information to the word,
such as –s on runs, which tells us that it is 3rd person
singular present tense verb, or the –s on
boys, which tells us that there is more than one boy.

There are eight inflectional suffixes, often just called “inflections,”” in
English:

-s on verbs: 3rd person sg, present tense (he runs, she walks)
-ed on verbs: past tense: (I walked, they joined)
-ing on verbs: progressive (I was walking; they were joining)
-en on verbs: past participle (I was beaten; she has eaten)
-s on nouns: plural (boys, books)
-‘s on nouns; possessive (boy’s, book’s)
-er on adjectives: comparative (quicker, slower)
-est on adjectives: superla

Several of these inflections are similar phonologically, but do not confuse them.
The –s on the end of 3rd person singular verbs, the –s plural on
nouns, and the -‘s possessive ending are the same purely by
coincidence. Also, do not confuse the –ing inflectional ending used to
make verbs progressive (“I am singing”) with the derivational morpheme –ing
used to make verbs into nouns (“Singing is a fun thing to do”). They sound the same,
but they are used differently. Finally, do not let spelling confuse you. We signify
possessive plurals in spelling by adding an apostrophe to the end of the word
(e.g., boys’) but the only inflectional ending here is the s-plural. The apostrophe
is just a spelling convention.

Content vs Function Morphemes

There is one final distinction between different kinds of morphemes:

content morphemes, which have a clear semantic meaning (like book,
luck, un-, –y, boy)
function morphemes, which include all inflectional morphemes like –s, and
–ed, but also include free morphemes such as the, of,
with, and, but, and other similar words. These words
signify the grammatical relationships between words and give structure to a
sentence.

The wikipedia page on function words
has an excellent example of the difference
between content words and function words. Read these two sentences:

The winfy prunkilmonger from the glidgement mominkled and brangified all
his levensers vederously.
Glop angry investigator larm blonk government harassed gerfritz infuriated
sutbor pumrog listeners thoroughly.

In the first sentence, all the content words have been replaced with nonsense
words, but notice how the grammatical structure of the sentence is still clear.
You can tell that winfy is an adjective, that the words mominkled
and brangified are past tense verbs, and so on. In the second sentence
the content words are English but the function words have been replaced.
Without clear function words, this
sentence has no clear grammatical structure and is entirely incomprehensible!

Allomorphs

Allomorphs are non-meaningful variants of a morpheme. For example, the -s plural
takes three distinct phonological forms, [s], [z], and [ɪz], in the words
boys [bɔɪz], books [bʊks], and dishes [dɪʃɪz]. These
phonological distinctions are considered non-meaningful, making these allomorphs
of the -s plural morpheme.