English Words

5.2.1
Selecting underlying representations
I argued earlier that by setting up a single underlying representation from which different allomorphs of a
morpheme are derived by phonological rules we are able to capture generalisations about the phonological
behaviour of morphemes. The distribution of the different allomorphs of a morpheme is normally not
arbitrary. We saw, for example, that voice assimilation is the principle behind the different allomorph guises
ENGLISH WORDS 61

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adopted by the /-z/ plural suffix. The idea of generality is vital. It is the principle that led us to posit /-z/ as
the underlying representation from which the allomorphs /-z/, /Iz/ and /-s/ are derived.
Often the same phonological factor that determines the morphophonemic alternations of one morpheme
is also relevant in alternations of several other morphemes. Therefore what is needed is a solution that
enables us to make a general statement of phonological conditioning which is valid for several morphemes.
For instance, if you look at the suffix of the third person singular present tense forms of verbs, you will see
that it shows exactly the same alternations as the /-z/ plural suffix of nouns. If we made separate statements
for these two morphemes we would be missing this generalisation.
[5.4]
Phonologically conditioned allomorphs of the third person singular
a.
Underlying /-z/ is realised as /-s/ if a stem ends in a voiceless consonant which is
not a strident coronal. This means that /-s/ is added after /p t k f /.
Underlying representation
Surface representation
skips
/skIp-z/
/skips/
lights
/laIt-z/
/laIts/
likes
/laIk-z/
/laIks/
laughs /la:f-z/
/la:fs/
baths
/ba: -z/
/ba: s/
b.
Underlying /-z/ is realised as /-z/ if a stem ends in a voiced sound which is not a strident coronal. This
means that /-z/ is added after the consonantal segments /b d g v m n l r w/ and after any vowel, e.g.: 
Underlying representation
Surface
representation
roams
/reum-z/
/reUmz/
calls
/k:l-z/
/k:lz/
skids
/skId-z/
/skIdz/
brags
/bræg-z/
/brægz/
sees
/si:-z/
/si:z/
shows
/ eU-Z/
/ eUz/
c.
Underlying /-z/ is realised as /-Iz/ if a stem ends in a consonant which is both strident
and coronal.
This means that /-Iz/ is added after the consonantal segments, /s z t d/, with /I/ being
inserted to separate coronal sibilants. (See p. 85 above.)
Underlying representation
Surface
representation
misses
/mIs-z/
/mIs-Iz/
/mIsIz/
wishes
/wI -z/
/wI -IZ/
/wi iz/
launches /l:nt -z/
/l:nt -Iz/