# Towards a typology of unitization: noun classes, classifiers, singulatives

Frank Seifart

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## To cite this version:

Frank Seifart. Towards a typology of unitization: noun classes, classifiers, singulatives. Ines Fiedler; Lee J. Pratchett. Areas, families, and pools aplenty: a Festschrift for Tom Güldemann, Humboldt-Universität zu Berlin, pp.445-455, 2025, 10.18452/32596. hal-05145031

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# Towards a typology of unitization: noun classes, classifiers, singulatives

## 1 Introduction<fnref n="1" />

Most, if not all, languages have morphosyntactic devices to “unitize” mass nouns and collective nouns, including constructions such as *one pound of flour*, *one head of cattle* in English and singulative markers in other languages. This chapter offers some thoughts on the cross-linguistic variation among grammatical unitization strategies, based on a comparison of an Amazonian noun class system (section 2) with singulatives (section 3) and numeral classifiers (section 4). While the descriptive facts compared here have been known for some time, their comparison in a single framework offers a new perspective in the context of a growing interest in the intersection of classification, countability, and number marking (e.g., Güldemann & Fiedler 2021; 2022). The current paper proposes eight parameters for a typology of unitization (section 5) related to (i) the set of nouns that unitization applies to, (ii) the set of unitizing elements, (iii) the locus of unitizing elements, and (iv) interaction with number marking.

The terminology used here mostly follows Rijkhoff (2002) in distinguishing, within count nouns, singular object nouns from collective nouns and transnumeral nouns (“set nouns” in Rijkhoff’s [2002] terms), which may refer to any number of individual, countable referents, including single referents. Within non-count nouns, mass nouns are distinguished from sort nouns (also called “concept nouns”). In individual languages, these lexical-semantic noun types may—or may not—be distinguished by

<footnote>* Corresponding author: Frank Seifart, CNRS-SeDyL. E-mail: frank.seifart@cnrs.fr.

To be cited as: Seifart, Frank. 2025. Towards a typology of unitization: noun classes, classifiers, singulatives. In: Ines Fiedler and Lee J. Pratchett (eds.), *Areas, families, and pools aplenty: a Festschrift for Tom Güldemann*, 445-454. Berlin: Humboldt-Universität zu Berlin. DOI: 10.18452/32596.

Appears in: Fiedler, Ines and Lee J. Pratchett (eds.). 2025. *Areas, families, and pools aplenty: a Festschrift for Tom Güldemann*. Berlin: Humboldt-Universität zu Berlin. DOI: 10.18452/31543</footnote>

<footnote n="1">¹ Jan Rijkhoff, Walter Bisang, Nick Enfield, Nikolaus Himmelmann, Bernhard Wälchli, and Ines Fiedler’s comments are gratefully acknowledged, as well as DFG funding no. SE 1949/5-1.</footnote>
distributional restrictions in, e.g., counting constructions or pluralization. The term “unitization” is used here for the formation of a singular object noun (or a noun phrase with these properties) from any other noun type, including collective or transnumeral nouns. Unitization thus always involves the specification of singular number, and possibly—when applied to a mass or sort noun—additionally the specification of an individual unit.

## 2 Miraña noun classes

Miraña [mira1254] is a Boran language, closely related to Bora proper [bora1263] (Thiesen & Weber 2012), spoken in the Northwest Amazon. The data discussed here are from Seifart (2005). Miraña has a set of nouns that cannot combine with the inflectional number markers that other nouns take and that may refer to substances (example 1),<fnref n="2" /> multiple individuals (example 2), or both (3). From these nouns, singular object nouns can be derived with what Seifart (2005) calls “class marker” suffixes, and these nouns take obligatory plural marking when plural in reference (1b–c, 2b–c, 3b–c).

(1) a. *ímu*
‘earth’

b. *ímu-ba*
earth-CL.LUMP
‘a piece of earth’

c. *ímu-bá-*nɛ
earth-CL.LUMP-PL
‘pieces of earth’

(2) a. *ka:*
‘ants’

b. *ka-?ba*
ants-CL.LUMP
‘an ant’

c. *ka-?bá-*mu
ants-CL.LUMP-PL.ANIM
‘some ants’

(3) a. *ko:*
‘wood/logs’

b. *ko-?ba*
wood-CL.LUMP
‘a log’

c. *ko-?bá-*nɛ
wood-CL.LUMP-PL
‘logs’

Class markers in Miraña are a heterogeneous set of about 70 forms defined by exclusive occurrence in a number of morphosyntactic contexts, among them numerals. Class markers range from short, semantically general, and highly frequent forms, such as -*(?)*ba in examples 1–3, to longer and less frequent forms, such as -*hu:*?o CL.PALMLEAF. These mostly shape-denoting “specific” markers are used mostly for inanimates, but included in the set are also six “general class markers” that distinguish animacy, gender, and number. An additional set of so-called “repeaters” can be used as free forms as well as in slots otherwise reserved for class markers. Overall, this inventory is reminiscent of numeral classifiers with respect to the size of the inventory, its

<footnote n="2">² Abbreviations: ANIM - animate, CL - classifier or noun class marker, COP - copula, INAN - inanimate, M - masculine, PL - plural, SG - singular.</footnote>
semi-openness (through repeaters) and the semantic profile, with natural gender for animates and shape for inanimates as predominant semantics.

Besides noun derivation (examples 1–3), class markers are used for agreement marking, including on numerals (example 4). On numerals, no specific class marker other than the one already present on the noun may be used, even if in a given situation it would be semantically more appropriate, e.g. if an avocado fruit happens to be oblong (example 4b). This confirms that on numerals, class markers are used for agreement marking, not for specifying a unit.

(4) a. *íhka-ba* tsa-ʔba *múhuu-ba* kó:huu-ba
COP-CL.LUMP one-CL.LUMP big-CL.LUMP avocado-CL.LUMP
‘There is one big avocado.’

b. \*tsa-ʔo kó:huu-ba
one-CL.OBLONG avocado-CL.LUMP

Which noun types does unitization in Miraña apply to? Unlike in other languages, the combinability of nouns with quantifiers does not differentiate nouns that refer to masses from those that refer to collectives (example 5): Noun class agreement on quantifiers is marked with the “general inanimate class marker” -nɛ and there is no number agreement. Non-unitized nouns denoting ethno-zoological species, however, may also take animate plural, but not singular agreement (examples 6), suggesting that these form a subclass of collective nouns within non-unitized nouns.

(5) a. *míta-nɛ́* tnu b. *míta-nɛ́* ka:
big/much/many-CL.INAN earth big/much/many-CL.INAN ants
‘much earth/dirt’ ‘many ants’

(6) a. *tsá-mɛ́* ka: b. \*tsa-bɛ́ ka:
come-CL.ANIM.PL ants come-CL.M.SG ants
‘(the) ants came’

More evidence for differentiating noun types can be gained from the combinability of non-unitized nouns with various, different class markers. The great majority of ethno-zoological terms (examples 2, 6) can only combine with one class marker, indicating that these are pre-specified for the one particular unit that is denoted by the derived unitized noun, and confirming their status as individuated collective nouns. Other, mostly inanimate nouns, but also some animate nouns, can combine with various class markers, specifying different individual units that are related to the
meaning of the underived, non-unitized noun (examples 7–8). For these nouns, the underived, non-unitized noun (example 7a, 8a) can refer to a non-singular number of objects denoted by the derived nouns, as well as—in the case of inanimate nouns (example 7a)—to a substance. In examples 7–8, unitization thus involves the specification of a unit in addition to singular number, although it still remains unclear whether there is any formal difference between non-individuated and collective nouns in Miraña.

(7) a. **whi**
‘banana substance/fruits/plants/plantations/bunches/seeds/etc.’

b. **whi-?o**
banana-CL.OBLONG
‘banana fruit’

c. **úhi-hi**
banana-CL.DISC
‘seed of a species of wild banana’

d. **whi-?i**
banana-CL.BUNCH
‘banana bunch’

e. **úhi-ba**
banana-CL.LUMP
‘banana drink’

(8) a. **méníkɛ**
ants
‘ants’

b. **méníkɛ-wu**
ants-CL.ROUND
‘ant’

c. **méníkɛ-mi**
ants-CL TRANSPORT
‘anthill’

In some languages, there are distinct mensural vs. sortal classifiers that also distinguish mass nouns from sort nouns (see Section 4). Some Miraña class markers have meanings comparable to those of mensural classifiers (example 9), but there is no distributional difference between these and other class markers. In fact, many class markers can be used like mensural classifiers, including those that are otherwise used to simply singularize collective nouns (example 10). This indicates again the lack of a formal difference between unitization of non-individuated (mass, sort, or general) nouns and that of individuated collective nouns.

(9) a. **píka-ʔdáʔi**
manioc-CL.PIECE
‘a piece of manioc’

b. **úme-htsú-ʔo**
salt-CL.BUNDLE
‘bundle of salt’

(10) a. **úme-gwa**
salt-CL.PLANK
‘plank-shaped piece of salt’

b. **míkúru-gwa**
stars/fireflies-CL.PLANK
‘star/firefly’
How are non-unitized nouns distributed across the Miraña lexicon? A comprehensive dictionary of the closely related Bora (Thiesen & Thiesen 1998) includes close to 3,000 non-unitized (including “absolute” and “collective”) nouns but only about 1,250 singular object nouns. There are many non-unitized nouns among inanimate nouns (examples 1a, 3a, 7a), some among ethno-zoological terms (examples 2a, 8a), and only very few among human nouns, as expected from the prediction that “the singular-plural distinction in a given language must affect a top segment of the Animacy Hierarchy” (Corbett 2000: 56; see also Smith-Stark 1974).

## 3 Singulatives

Singulatives are morphological markers that turn non-unitized nouns into singular object nouns (Corbett 2000; Dali & Mathieu 2021; Nurmio 2023). I first discuss Breton (Celtic) [bret1244], and then Afro-Asiatic languages. In Breton most nouns are singular object nouns that obligatorily take the suffix -où in plural (Press 2004). These are distinguished from non-unitized nouns that cannot usually combine with the plural suffix, with numbers or some quantifiers and modifiers (Press 2004: 39). Some of these nouns have collective reference (example 11), some mass reference (example 12), and some can have both (example 13). Collective nouns and mass nouns can be formally distinguished by the number agreement they take: Collective nouns take plural agreement and mass nouns take singular agreement (Press 1986: 69). Singular object nouns are formed from both subtypes of non-unitized nouns by suffixing the invariable singulative marker -enn (examples 11b, 12b, 13b). Singulative-marked nouns obligatorily take plural marking when plural in reference (examples 11c, 12c, 13c), confirming their status as singular object nouns. If the basic, underived form is collective, the plural form refers to a smaller group than the non-unitized noun (examples 11a vs. c, 13a vs. c).

(11)a. *per*
'pears'

b. *per-enn*
'pear'

c. *per-enn-où*
'some pears'

(12)a. *ed*
'wheat'

b. *ed-enn*
'grain of wheat'

c. *ed-enn-où*
'some grains of wheat'

(13)a. *kistin*
'chestnut (timber)
or chestnuts'

b. *kistin-enn*
'chestnut'

c. *kistin-enn-où*
'some chestnuts'
Number marking in Afro-Asiatic languages can be complex, with different, partially overlapping patterns in different sections of the nominal lexicon (Frajzyngier 2018). In some of these patterns, singulatives occur that form singular object nouns from non-unitized nouns, as in Cushitic Arbore [arbo1245] (examples 14–16, from Hayward 1984: 161–162). Unlike in Celtic languages, unmarked forms in Arbore are often transnumeral and there can be two, or more, singulative markers (example 16), rather than a single one (see also Stroomer [1987: 86] on Cushitic Oromo languages [nucl1701]).

(14)a. lássa
‘bread’

b. lassa-n
‘a bread loaf’

(15)a. tiísi
‘maize cob(s)’

b. tiisi-in
‘a maize cob’

(16)a. nebel
‘ostrich(es)’

b. nebel-in
‘a cock ostrich’

c. nebel-inté
‘a hen ostrich’

As already noted by Greenberg (1963), singulative marking always applies only to a part of the nominal lexicon. In both Celtic and Cushitic languages this is only a minor subset of nouns. In Breton, for instance, 4–6% of nouns are collective nouns according to Favereau (1997: 33), and mass nouns—for which there are no separate counts available—are presumably also only a minor part or the nominal lexicon.

## 4 Numeral classifiers

Numeral classifiers are found with relatively uniform characteristics in hundreds of languages across the world (Aikhenvald 2000: 98–124; Her, Hammarström & Allassonnière-Tang 2022). Examples 17–18 (from Li & Thompson 1981) illustrate numeral classifier unitization in Mandarin Chinese [mand1415], which is very similar to other East and South East Asian languages (Bisang 1999; Her & Li 2023). All Mandarin Chinese nouns can be used without further marking to refer to unspecified numbers of objects (example 17a) or to masses (example 18a). These nouns cannot take plural marking, which is unsurprising because there is no inflectional plural marking at all in the language. In numeral constructions, these nouns are obligatorily unitized with one out of a few dozen numeral classifiers (example 17b, 18b).

(17)a. fēiji
‘airplane(s)’

b. wǔ jià
five CL.MACHINE
‘five airplanes’

fēiji
airplane(s)
(18)a. ròu
'meat'

b. shí
'ten
'ten pounds of meat'

Numeral classifiers also occur in contexts other than numerals in Mandarin Chinese, primarily with demonstratives, as in other languages. The distinction between numeral classifiers and nouns is often not clear-cut: In Mandarin Chinese, classifiers can be analyzed as a subclass of nouns (Sackmann 2000) and Vietnamese [viet1252] classifiers are argued to be a syntactic position rather than a word class separate from nouns (Löbel 2000). Mandarin Chinese sortal numeral classifiers (example 17) impose a classification on the nominal lexicon based on animacy and physical properties, such as shape, dimensionality, and arrangement (Croft 1994: 152; Aikhenvald 2000: 286–293; Grinevald 2000: 72–73). Mensural classifiers (example 18) combine more freely with nouns, specifying different measures.

Some authors argue that sort nouns in numeral classifier languages lack specifications of a unit in their lexical semantics, and that the meaning of fēiji 'airplane(s)' would be the “concept” of an airplane (Lucy 1992; Rijkhoff 2002; Bale & Barner 2018). Others argue that such nouns are transnumeral and denote an unspecified number of a particular unit, which is redundantly expressed in the classifier (Croft 2001: 119–129). Unitization with a specification of a unit, in addition to singular number, would then only occur with mensural classifiers. In any case, sortal and mensural unitization appear to be morphosyntactically identical in numeral classifier languages (examples 17-18), even if a difference between sortal and numeral classifiers can be established through distributional tests carried out on the classifiers in contexts other than counting (see Sackmann 2000 for Mandarin Chinese; Löbel 2000 for Vietnamese; Hundius and Kölver 1983 for Thai [thai1261]). Other numeral classifier languages, such as Yucatec Maya [yuca1254] (Lucy 1992), appear to not formally differentiate sortal classifiers from mensural classifiers, or count nouns from mass nouns, at all.

Two universals have been proposed about numeral classifiers that are related to their unitizing function: Firstly, they always form a phrase with the numeral and are always adjacent to it, but not necessarily adjacent to the noun (Greenberg 1977: 293). Secondly, they never co-occur with obligatory plural marking in the same phrase (Sanches and Slobin 1973; Greenberg 1977). This incompatibility may apply to languages as a whole, like Mandarin Chinese, or to different sections of the nominal lexicon, as in Yucatec Maya (Smith-Stark 1974; Lucy 1992).
## 5 Towards a typology

Table 1 compares the unitization strategies discussed here along a set of eight parameters. Regarding the nouns that unitization applies to (parameters 1–3), all three strategies are used in much the same way to specify units for non-individuated mass and possibly sort nouns and to mark singular number for collective or transnumeral nouns. These two processes are often viewed as fundamentally different (e.g., Bale & Barner 2018), but this difference is not reflected in the morphosyntax of the strategies considered here.

<table><caption>Table 1 Parameters for a typology of unitization</caption><thead><tr><th></th><th>typological parameter</th><th>Singulatives</th><th>Class markers</th><th>Numeral classifiers</th></tr></thead><tbody><tr><td rowspan="3">nouns</td><td>1 individuation of non-individuated nouns</td><td>yes</td><td>yes</td><td>yes</td></tr><tr><td>2 singularization of collective and/or transnumeral nouns</td><td>yes</td><td>yes</td><td>yes</td></tr><tr><td>3 portion of nominal lexicon that unitization applies to</td><td>small</td><td>large</td><td>very large</td></tr><tr><td>unitizers</td><td>4 large set of unitizing forms with classificatory effect</td><td>no</td><td>yes</td><td>yes</td></tr><tr><td rowspan="3">locus</td><td>5 occurrence on numerals</td><td>no</td><td>yes</td><td>yes</td></tr><tr><td>6 unitization on numerals</td><td>no</td><td>no</td><td>yes</td></tr><tr><td>7 unitization directly on nouns</td><td>yes</td><td>yes</td><td>no</td></tr><tr><td>plurals</td><td>8 co-occurrence with plural marking</td><td>yes</td><td>yes</td><td>no</td></tr></tbody></table>

Parameters 3–8 set numeral classifiers apart from singulatives, but some of them are shared with Miraña noun class markers (parameters 3–5): both are large sets for forms that apply to large sections of the nominal lexicon with a classificatory effect. Numeral classifiers and Miraña noun classes also share the characteristic that the unitizing elements occur with numerals (parameter 5). However, there is a crucial difference in the function of classifiers or class markers in combination with numerals: numeral classifiers unitize nouns in combination with numerals, but Miraña noun classes mark agreement on numerals and do not unitize nouns in these constructions (parameter 6). Regarding the locus of the unitizing function, Miraña noun classes pattern with singulatives: in both types of strategies, unitization takes place on the nouns themselves (parameter 7). Miraña also shares with singulatives that unitization co-occurs with number marking within the same phrase, again setting these two strategies apart from numeral classifiers (parameter 8). Consequently, the typological claim that classifiers (or class markers) in
numeral constructions never co-occur with obligatory plural marking (Sanches and Slobin 1973; Greenberg 1977) must be constrained to classifiers (or class markers) that perform their unitizing function in numeral constructions, not elsewhere.

The addition of Miraña class markers to the comparison of singulatives and numeral classifiers reveals, on the one hand, that large sets of unitizing classifiers or class markers are not restricted to numeral constructions but may occur directly on nouns. On the other hand, unitization that takes place on nouns directly may apply beyond a minor subset of nouns and involve many different forms with a classificatory effect. The parameters posited here thus vary independently in a multidimensional typological space in which three types of strategies emerge as partially overlapping clusters. Two of these, singulatives and numeral classifiers, are known to be recurrent types of strategies in the world's languages. Regarding the third, class marker unitization, we still do not know. More research is also needed regarding the position within this typological space of other still less well described strategies involved in unitization, including those occurring in concurrent and transitional systems (Güldemann & Fiedler 2021; Saikia & Allassonnière-Tang 2023).

## References

Aikhenvald, Alexandra. 2000. Classifiers. A typology of noun categorization devices. Oxford: Oxford University Press.

Bale, Alan & David Barner. 2018. Quantity judgment and the mass-count distinction across languages: Advances, problems, and future directions for research. Glossa: a journal of general linguistics 3(1): 63. 1–23.

Bisang, Walter. 1999. Classifiers in East and Southeast Asian languages. Counting and beyond. In Jadranka Gvozdanović (ed.), Numeral Types and Changes Worldwide, 113–185. Berlin: Mouton de Gruyter.

Corbett, Greville. 2000. Number. Cambridge: Cambridge University Press.

Croft, William. 1994. Semantic universals in classifier systems. Word 45(2): 145–171.

Croft, William. 2001. Radical Construction Grammar. Oxford: Oxford University Press.

Dali, Miriam & Eric Mathieu. 2021. Singulative Systems. In Patricia Cabredo Hofherr & Jenny Doetjes (eds.), The Oxford Handbook of Grammatical Number, 275–290. Oxford: Oxford University Press.

Frajzyngier, Zygmunt. 2018. Afroasiatic Languages. In Oxford Research Encyclopedia of Linguistics. Oxford: Oxford University Press.

Greenberg, Joseph. H. 1963. Some universals of grammar with particular reference to the order of meaningful elements. In Joseph H. Greenberg (ed.), Universals of human language, 73–113. Cambridge, MA: MIT Press.

Greenberg, Joseph. H. 1977. Numeral classifiers and substantival number: Problems in the genesis of a linguistic type. In Adam Makkai, Valerie Becker Makkai & Luigi Heilmann (eds.), Linguistics at the Crossroads, 276–300. Padova: Liviana Editrice.
Grinevald, Colette. 2000. A morphosyntactic typology of classifiers. In Gunter Senft (ed.), *Systems of Nominal Classification*, 50–92. Cambridge: Cambridge University Press.

Güldemann, Tom & Ines Fiedler. 2021. More diversity enGENDERed by African languages: an introduction. *STUF - Language Typology and Universals* 74(2). 221–240.

Güldemann, Tom & Ines Fiedler. 2022. Restructured Niger-Congo gender systems as another type of concurrent nominal classification. *Journal of African Languages and Linguistics* 43(2). 139–163.

Hayward, Dick. 1984. *The Arbore language: a first investigation, including a vocabulary*. Hamburg: Buske.

Her, One-Soon & Bing-Tsiong Li. 2023. A single origin of numeral classifiers in Asia and the Pacific: A hypothesis. In Marc Allassonnière-Tang & Marcin Kilarski (eds.), *Nominal Classification in Asia and Oceania: Functional and diachronic perspectives*, 113–160. Amsterdam: John Benjamins.

Her, One-Soon, Harald Hammarström & Marc Allassonnière-Tang. 2022. Defining numeral classifiers and identifying classifier languages of the world. *Linguistics Vanguard*. 8(1). 151–164.

Hundius, Harald & Ulrike Kölver. 1983. Syntax and semantics of numeral classifiers in Thai. *Studies in Language* 7(2): 165–214.

Li, Charles N. & Sandra A. Thompson. 1981. *Mandarin Chinese: A functional reference grammar*. Berkeley CA: California University Press.

Löbel, Elisabeth. 2000. Classifiers versus genders and noun classes: A case study in Vietnamese. In Barbara Unterbeck & Matti Rissanen (eds.), *Gender in Grammar and Cognition*, 259–319. Berlin: Mouton de Gruyter.

Lucy, John A. 1992. *Grammatical categories and cognition. A case study of the linguistic relativity hypothesis*. Cambridge: Cambridge University Press.

Nurmio, Silva. 2023. Towards a typology of singulatives: Definition and overview of markers. In Deborah Arbes (ed.), *Number Categories: Dynamics, Contact, Typology*, 155–182. Berlin: De Gruyter Mouton.

Press, Ian. 2004. *Standard Breton*. Munich: Lincom Europa.

Rijkhoff, Jan. 2002. *The Noun Phrase*. Oxford: Oxford University Press.

Sackmann, Robin. 2000. Numeratives in Mandarin Chinese. In Petra M. Vogel & Bernard Comrie (eds.), *Approaches to the Typology of Word Classes*, 421–477. Berlin, New York: Mouton de Gruyter.

Saikia, Pory & Marc Allassonnière-Tang. 2023. Nominal classification in Assamese. In Marc Allassonnière-Tang & Marcin Kilarski (eds.), *Nominal Classification in Asia and Oceania: Functional and diachronic perspectives*, 30–55. Amsterdam: John Benjamins.

Sanches, Mary & Linda Slobin. 1973. Numeral classifiers and number marking: An implicational universal. *Working Papers in Languages Universals, Stanford University* 11: 1–22.

Seifart, Frank. 2005. *The structure and use of shape-based noun classes in Miraña (North West Amazon)*. Nijmegen: Max Planck Institute for Psycholinguistics.

Smith-Stark, Thomas C. 1974. The plurality split. In Michael W. La Galy, Robert A. Fox & Anthony Bruck (eds.), *CLS 10, 657–671*. Chicago: Chicago Linguistic Society.

Stroomer, Harald. 1987. A comparative study in three southern Oromo dialects in Kenya: phonology, morphology, and vocabulary. Hamburg: Buske.

Thiesen, Wesley & David Weber. 2012. *A grammar of Bora with special attention to tone*. Dallas: SIL International.

Thiesen, Wesley & Eva Thiesen. 1998. *Diccionario Bora - Castellano, Castellano - Bora*. Yarinacocha: Instituto Lingüístico de Verano