Phonological Alternations

Phonological alternations in Sereer are differently characterized depending on the portion of the word they occur in. On the one hand, Sereer has stems that are fairly invariant in size, almost exclusively alternating by way of morphologically determined consonant mutation of initial (or sometimes final) segments. On the other hand, affixes (and especially verbal suffixes) have phonologically determined allomorphs that alternate between the segmental shapes -VC and -C, seemingly motivated by an avoidance of overlong consonant clusters and hiatus. There is a trade-off in phonological content, then, between invariance in terms of shape (in stems, whose segments do change) and invariance in terms of segments (in affixes, whose shape does change).

Stem Morphophonology

Sereer has salient alternations in the initial consonants of noun and verb stems. These alternations appear to be morphologically conditioned in a lexically specified manner, since they occur in several different segmental contexts whose only common element is being within a morphologically derived environment (e.g. plurality in both nouns and verbs; addition of apparent nominalizing suffixes to verbs).

Standard nominal mutation

With one exception (the alveolar fricative s), the standard nominal mutation pattern is between homorganic segments. Voiced modal stops, prenasalized stops, and fricatives become voiceless modal stops in plural nouns; voiced implosives become voiceless implosives; labial and alveolar approximants /w/ and /r/ become voiced and voiceless modal stops, respectively. All other consonants are invariant between singular and plural forms.

Source consonant class	Mutated consonant	Labial	Alveolar	Palatal	Velar	Uvular	Glottal
fricative	voiceless stop	f > p		s† > c		x > q
prenasalized stop	voiceless stop	mb > p	nd > t	nj > c	ng > k	nq > q
voiced stop	voiceless stop	b > p	d > t	j > c	g > k
alveolar approximant	voiceless stop		r > t
voiced implosive	voiceless implosive	ɓ > ƥ	ɗ > ƭ	ʄ > ƈ
labial approximant	voiced stop	w > b
voiceless stop	-	p	t	c	k	q	'
voiceless implosive	-	ƥ	ƭ	ƈ
palatal/lateral approximant	-		l	y
nasal	-	m	n	ñ	ŋ

^†The consonant s is a partial exception to the regularity of the standard nominal mutation, as it is sometimes invariant and sometimes not. When it alternates (on a lexically-determined basis), it does so with the voiceless palatal stop c. See s alternations for more information.

The standard nominal mutation is most commonly seen in the singular-plural alternations of nouns in most noun classes. For all noun classes except the ox/w and al/ak classes, plural number is indicated by the mutation of the initial consonant of the noun stem, as well as the initial consonant of stems of any adjectives and determiners. For the ox/w class, it is the singular number that is indicated by this mutation, with the plural number evincing the basic form of the stem.

Gloss	Noun class	Noun	Det.
pig pigs	l ak	ruul atuul	le ake
rabbit rabbits	n k	ndool tool	ne ke
woman women	ox w	otew rew	oxe we
trip trips	al ak	atex atex	ale ake

Affective noun classes

Diminutives/augmentatives ("affectives") also exhibit initial segment mutations relative to the non-affective noun category. Further generalizations await.

Nouns

(discussion on sg./pl. alternations here)

Deverbal nouns: A noun can be formed from (any?) verb by affixing a prefix a- to the verb root, and altering the initial consonant of the root.

verb	meaning	noun	meaning
ret	go	atet	a trip, "going"
ɗing	fence (in)	aƭing	fence
tos	gather manure	atos	pile of manure
piis	draw a line	apiis	line
weʄ	swim	abeʄ	a swim, swimming

Further alternations remain to be seen, but it appears that the same sorts of alternations seen elsewhere in the language are present here (r,d > t ; voiced implosive > voiceless implosives, etc.)

There are some less straightforward alternations involving not only the initial consonant:

rain (v): deɓ
rain (n): ateƥ

slap (v): faɗ
slap (n): ombaƭ

Verbs

The initial consonant of verb roots can vary based on whether the subject is singular or plural. Non-implosives alternate with prenasalized stops, and implosives alternate with their voiceless counterparts. Alternations are mostly, but not completely, predictable (note multiple possible alternations for /s/ and /q/).

sg.~pl.
f~mb
b~mb
w~mb
ɉ~ɲɉ
χ~ɴɢ
ɗ~ƭ
ɓ~ƥ
ʄ~ƈ
r~nd
d~nd
g~ng

Invariant:
j~j
l~l
m~m
n~n
ŋ~ŋ
ɲ~ɲ
p~p
t~t
k~k
c~c
s~s
ʔ~ʔ

We still need to get the sg vs. pl. forms of verbs starting with:
q

It seems that verb roots (as seen with singular subjects) cannot start with voiceless implosives or prenasalized stops.

Postverbal Affixes

A number of postverbal affixes exhibit a morphophonological alternation between a -VC and -C form. The -VC form appears between consonants, or after a consonant at the end of word, and the -C form appears elsewhere.

1st sg. subject: -(u)m

gef-aa-m 'I break'
vs.
gef-aa-n-um 'I break it'

2nd sg. object: -(o)ng

3rd sg. object: -(i)n

Causative: -(i)n

Reciprocal: -(i)r

Itive: -(i)k

Instrumental applicative: -(i)t

Reversive: -(i)t