AbstractIn this paper we provide a descriptive account of the interacting morphological, phonological, and lexical factors determining how diminutives are marked in Tiania [etianíá], an understudied variant of the Central Kenya Bantu language Kimeru. As in other languages, diminutivization in Tiania can indicate a decrease in size or quantity or express positive endearment or negative scorn, depending on the noun and the context. We will show that diminutivization is effected by transferring nouns into singular noun class 12 and plural class 13, as in other Bantu languages, but with two interesting variations: First, depending on the lexical class of the input noun, the diminutive prefixes will either replace or precede the noun’s prefix. In the latter case, the diminutive plural prefix may be added to either the singular or plural form of the base noun, again depending on the latter’s noun class. The second interesting variation is that the majority of nouns which have an /r/ in their stem or prefix replace such /r/’s by [l], something we refer to as “expressive lateralization”, e.g. e-rinyá ‘pit, cave (class 5)’ → ka-linyá ‘a small pit (class 12)’, ri-étwa˚ ‘name (class 5)’ → ka-li-étwa˚ ‘a sweet name’. To study the first variation, we systematically survey the diminutivization of nouns from all noun classes, singular and plural. To study the second variation, we track every one of 330 nouns with /r/ with respect to lateralization. In attempting to explain why such lateralization should occur, we consider augmentative and depreciative noun to noun derivations which also undergo /r/ → [l] as well as other derived word classes, e.g. adjectives, which sometimes undergo expressive lateralization, depending on whether they are denominal or deverbal (verbs never show such effects). Being that this is the only reported case we know of expressive lateralization, Tiania is both of typological interest as well as a mystery within Bantu and beyond.