S alternations

The consonant s behaves unexpectedly with regard to the consonant mutation processes in Sereer, for two reasons. First, it is the only consonant that mutates variably for a given mutation process. Second, it is the only mutating consonant that does not maintain its place of articulation, moving from an alveolar to a palatal place of articulation.

Standard nominal mutation

The sole exception to the regularity of the standard nominal mutation, s is sometimes invariant and sometimes not. When it alternates (on a lexically-determined basis), it does so with the voiceless palatal stop c.

English gloss	Singular	Plural
pile of millet husks	soxon	coxon
village	saate	caate
onion	soble'	soble'
boat	suk	suk

Historical conjecture

It is possible that the present-day Sereer phoneme s represents a convergence of two historical fricatives, <nonwiki>*</nonwiki>s and <nonwiki>*</nonwiki>ʃ. The lexical items beginning with s that now undergo standard nominal mutation may have originally been a palatal segment, explaining the changing place of articulation. Comparison of related languages will no doubt indicate the veracity of this conjecture.