Affixal morphology is employed by nearly all the world's languages to express modifications or specifications of the role or the meaning of a stem morpheme in its sentential context. 1 A single affix may appear fixed before, internal to, or at the end of the stem form (i.e., prefixing, infixing or suffixing), although the internal affix is extremely rare compared with prefixation and suffixation.2 When more than one morpheme at a time is fixed in prefix or suffix position, their order of proximity to the stem is highly constrained within languages. We therefore recognise two critical dimensions on which languages may vary: (i) the linear position of affixes relative to the stem (i.e. prefix or suffix), and (ii) the order of affixes relative to each other when they co-occur on the same side of the stem. Variation along the former dimension is exhibited across and within languages, but along the latter almost exclusively3 only across languages (i.e. a language may utilise different positions but not different orders). Bybee (1985) has shown that the ordering of affixes with each other is highly constrained across languages, and argues that this ordering follows universal principles of semantic relevance. For the present work, however, we are restricting our attention to cases of single affix occurrences and their positional preference with reference to the stem.