By desmond bett; B. A- criminology m. A – public administration & policy

b. *govern-abil-un-ity
c. *ity-un-abil-govern
d. *abil-un-ity-govern
e. *un-govern-ity-abil etc.

Clearly, knowing a word means not just knowing the morphemes it contains, but also the rigid order in which they are allowed to appear. We will return to this point in section (4.4).

To sum up the discussion so far, words are built using morphemes. If we know how morphemes are used to form words, we do not need to be unduly flustered when we come across a strange word. Usually it is possible to work out the meaning of a strange word if it contain familiar morphemes.

3.3
MORPHEMES AND THEIR DISGUISES
The identification of morphemes is not altogether straightforward. This is because there is no simple one-to-one correspondence between morphemes and the speech sound that represent them. In this section we will attempt to unravel the complexities of the relationship between morpheme and the actual forms (sound of groups of sounds) by which they manifested in speech.

3.3.1
Allomorphs: morph families
Any physical form that represents a morpheme is called a MORPH. The forms –ish, -less, -er, -s, re-, un- and ex- in [3.4] on p. 31 are all morphs. Morphological analysis begins with the identification of morphs, i.e. forms that carry some meaning or associated with some grammatical functions. In asparagus there is just one morph nut in all the words in [3.4] there are two.
This is not an abstruse distinction. We are not being pedantic. It is a distinction that matters to ordinary people because human languages are organized in such a way that the construction of units that are meaningful is normally in principle separate from the construction of strings that are pronounceable. Thus, for rhythmical effect, nursery rhymes often use nonsense syllables like ‘deedle, deedle’ in ‘Deedle deedle dumpling my son john’ which do not represent anything meaningful.
Alternatively, a sound representing a morpheme may not be a syllable in its own right, e.g. by itself, the –s which represents the plural morpheme is not a syllable. The word cats has two morphemes, cat and –s, but it is all just one syllable. The single syllable cats realizes two morphemes. The converse situation, where several syllables realize a single morpheme, is equally possible. Thus the trisyllabic and quadrisyllabic word-forms elephant and asparagus both just realize a single morpheme.
The nature of the relationship between sounds and morphemes is intriguing. At first sight, it might look reasonable to assume that morphemes are made up of PHONEMES. We might be tempted to think that cat, the English morpheme with the meaning is made up of the phonemes /kaet/. But we have several kinds of evidence showing that this is not the case.
First, if morphemes were made up of phonemes, a given morpheme would be uniquely associated with a given phonological representation. In reality, the same morpheme can be realized by different morphs (i.e. sounds of written forms). Morphs which realize the same morpheme are referred to as ALLOMORPHS of that morpheme.
The INFINITE ARTICLE is a good example of a morpheme with more than one allomorph. It is realized by the two forms a and an. The sound at the beginning of the following word determines the allomorph that is selected, but if it begins with a vowed the allomorph an is used instead:
[3.6]
a. a dictionary b. an island
a boat an evening
a pineapple an opinion
a leg an eye
a big (mat) an old (mat)
a dull (song) an exciting (finish)

Hence the incorrectness of the sentence marked with an asterisk in [3.7]:

[3.7]
a. I spent an evening with them.
*I spent a evening with them.
b. I spent the evening with them.

Allomorphs of the same morpheme are said to be in COMPLEMENTARY DISTRIBUTION. This means that they do not occur in identical contexts and therefore they cannot be used to distinguish meanings. In other words, it is impossible to have two otherwise identical utterances that differ in their meanings depending on the allomorph of morpheme that is selected. So, because a and an both realize the same indefinite article morpheme, it is impossible to have two sentences like those in [3.7a] above which are identical in all ways, except in the choice of a or an, but mean different things.

Complementary distribution presupposes the more basic notion of DISTRIBUTION. Distribution is to do with establishing facts about the occurrence of allomorphs of a particular morpheme. It is concerned with establishing the contexts in which the morpheme which we are investigating occurs and the allomorphs by which it is realize in those different contexts. In other words, by distribution we mean the total set of distinct linguistic contexts in which a given forms appears, perhaps in different guises. For instance, the indefinite article has the distribution: a before consonants (e.g. a tree) and an before vowels (e.g. an eagle).
As mentioned already, such functionally related forms which all represent the same morpheme in different environment are called allomorphs of that morpheme. Another way of putting it is that allomorphs are forms that are phonologically distinguishable which, none the less, are not functionally distinct. In other words, although they are physically distinct morphs with different pronunciation in the language.
An analogy might help to clarify this point. Let us compare allomorphs to workers who share the same job. Imagine a jobshare situation where Mrs. Jones teaches maths to form 2DY on Monday afternoon. Mr. kato on Thursday morning and Ms. Smith on Tuesday and Fridays. Obviously, these teachers are different individuals. But they all share the role of ‘maths teacher’ for the class and each teacher only performs that role on particular days. Likewise, all allomorphs share the same function but one allomorph cannot occupy a position that is already occupied by another allomorph of the same morpheme. To summarize, we say that allomorphs of a morpheme are in complementary distribution. This means that they cannot substitute for each other. Hence, we cannot replace one allomorph by another allomorph of that morpheme and change meaning.
For our next example of allomorphs we will turn to the plural morpheme. The ides of ‘more than one’ is expressed by plural morpheme using a variety of allomorphs including the following:
[3.8]
Singular plural

1. 
   rad-ius radi-i
   

cactus cact-i

2. 
   dat-um dat-a
   

strat-um strat-a

3. 
   Analys-is analys-es
   

ax-is ax-es

4. 
   skirt skirt-s
   

road road-s
branch branch-es
Going by the orthography, we can identify the allomorphs –I, -a, -es and –s . The last is by commonest: see section (7.3)
Try and say the batch of words in [3.8d] aloud. You will observe that the pronunciation of the plural allomorph in these words is variable. It is [s] in skirts, [z] in roads and [Iz] (or for some speakers [ez] in branches. What is interesting about these words is that the selection of the allomorph that represents the plural is determine by the last sound in the noun to which the plural morpheme is appended. We will return to this in more depth in section [5.2]
We have already seen, that because allomorphs cannot substitute for each other, we never have two sentences with different meanings which solely differ in that one sentence has allomorph X in a slot where another sentence has allomorph Y. compare the two sentences in [3.9]:
[3.9]
a. They have two cats b. They have two dogs
[eI have tu: kaet-s] [eI have tu: dg-z]
*[eI have tu: kaet-z] *[eI have tu: dg-s]

We cannot find two otherwise identical sentences which differ in meaning simply because the word cats is pronounced as [kaet-s] and *[kaet-z] respectively. Likewise, it is possible to have two otherwise identical sentences with different meanings where the word dogs is pronounced as [dgz] and *[dgs]. In other words, the difference between the allomorphs [s] and [z] of the plural morpheme cannot ne use to distinguish meanings.