Computational Modeling of Affixoid Behavior in C hinese Morphology (2020)

Abstract: The morphological status of affixes in Chinese has long been a matter of debate. How one might apply the conventional criteria of free/bound and content/function features to distinguish word-forming affixes from bound roots in Chinese is still far from clear. Issues involving polysemy and diachronic dynamics further blur the boundaries. In this paper, we propose three quantitative features in a computational model of affixoid behavior in Mandarin Chinese. The results show that, except for in a very few cases, there are no clear criteria that can be used to identify an affix’s status in an isolating language like Chinese. A diachronic check using contextualized embeddings with the WordNet Sense Inventory also demonstrates the possible role of the polysemy of lexical roots across diachronic settings.

## introduction in typological terms, mandarin chinese is a canonical isolating language. unlike other more agglutinative languages with rich derivational morphology and large numbers of highly productive affixes, mandarin words most often consist of either monosyllabic roots or polysyllabic, multi-root compounds @xcite . traditionally, a derivational affix is defined as a bound morpheme that attaches to a root or stem to change its syntactic category or contribute additional semantic content @xcite . however, the status of derivational affixes in chinese and the morphological processes that characterize them is still largely a matter of debate. morphological derivation and compounding are often contrasted with one another. despite this, defining a clear cross-linguistic distinction between the two processes can be troublesome. in languages such as english, a distinction between free and bound morphemes provides a relatively straightforward benchmark. a suffix like "-ology" is bound in english and must always attach to a root in order to productively derive new words in the language. on the other hand, free morphemes in english may combine together to form a compound, such as "green" and "house" in the english word "greenhouse". in mandarin, however, issues arise when free/bound and content/function criteria are used to distinguish word-forming affixes from bound roots, as these features are far from clearly defined in the language @xcite . issues involving polysemy and diachronic change further blur the boundaries @xcite @xcite . the morphological status of most chinese morphemes is indeterminate, which leads some to conclude that there is an extreme poverty of affixation in chinese morphology; it is rarely derivational and hardly ever inflectional. previous studies suggest so-called "pure" or "bona fide" affixes display high morphological productivity (i.e., are readily available for the formation of new words) as well as high syntactic productivity (i.e., may combine with stems to form various different parts of speech) @xcite . their meaning is less robust, and their position within the context of a word or sentence is generally more fixed @xcite . by contrast, a root will generally carry more substantial meaning, be subject to fewer positional constraints, and have lower morphological and syntactic productivity. somewhere in between these two poles are a class of words referred to by some in the literature as affixoids @xcite . this term has been used to describe a morpheme that behaves like an affix with respect to its high morphological and syntactic productivity and positional constraints, but semantically conveys a specific meaning that is both transparent to and yet distinct from another lexeme to which it corresponds formally and/or historically @xcite . however, some scholars argue against the delineation of affixoids as a separate class @xcite . in this study, we aim to empirically revisit this long-standing debate by way of computational modeling of affix(oid) behavior based on a comprehensive database of chinese. ## related works to date, only a few quantitative works measure affix behavior in chinese. most of them focus on quantifying the morphological productivity of a small number of chinese affixes. for instance, @xcite contrasts type-based and token-based measures, selecting five chinese suffixes for comparison: the nominal suffixes 兒 -ér, 子 -zi, and 頭 -tóu, the verbal suffix 化 -huà "-ize", as well as the plural suffix 們 -men "-s/-es". the latter is the only suffix of the four that may be considered an inflectional suffix in mandarin, while the other four are used productively in word formation, i.e., are derivational affixes. as a token-based measure, nishimoto uses baayen' s hapax-based measure @xcite , p , defined as @xmath0, where n 1 counts the number of hapax legomena of a particular affix in the corpus, and n represents the total number of occurrences of words containing the affix, i.e., a sum of word tokens containing the affix. dividing the number of hapax legomena by a total number of tokens containing the affix accounts for lexicalization of the affix. this follows the assumption that a large number of total tokens indicates a higher likelihood that the form has been lexicalized, which in turn can be said to reduce its productivity. in contrast, the type-based measure used in nishimoto's study does not take lexicalization into account. arcodia and basciano (2012) also apply baayen's p measure, focusing on just three of the derivational suffixes used in @xcite , namely 兒 -ér, 化 -huà, and 頭 -tóu. their results are consistent with those in nishimoto's study, providing evidence for the p index as a reliable measure of morphological productivity. ## modeling chinese affixoids based on previous studies, we propose three properties to characterize chinese affixoid 1 behavior. first, as word-forming devices, an affixoid tends to be morphologically productive. that is, an affixoid can occur in many different words. second, as a consequence of its productivity, the syntactic role of these words may vary across sentences. an affixoid may participate in various words with different parts-of-speech, and can involve a change in thematic role @xcite , making it also more syntactically productive. finally, productive affixoids tend to generate new words through imitations of already widely used word patterns. therefore, the meaning of the affixoid used to form new words is likely to remain consistent. the affixoid gradually loses much of its original meaning, that is, is semantically bleached, and therefore is less semantically diverse @xcite . we can formulate the general criteria from prior research as follows: if a bound morpheme carries mostly transpositional, non-inherent meaning, is not subject to a positional constraints (i.e., its position is not fixed), and has limited potential to form new words, it is best analyzed as a bound root; otherwise, it should be categorized as an affix. however, these qualitative means are insufficient to handle affixal polysemy. this is particularly an issue with respect to the debated status of wordhood (free lexical roots) in chinese. for instance, 手 shǒu "hand" behaves as a productive suffix in 鼓手 gǔ-shǒu drum-hand "drummer" or 水手 shuǐ-shǒu waterhand "sailor". in such contexts it carries less substantive meaning, but it cannot be said to occur in a fixed position, as it also occurs freely in word-initial position (e.g., 手銬 shǒu-kào hand-cuff "handcuff", 手環 shǒu-huán hand-ring "wristband"). clearly the above-mentioned tendencies (see also e.g., @xcite and packard ( 2000 )) are laden with descriptions that rely on scalar adjectives. however, a solely subjective treatment of affixoid behavior at the conceptual level, without anchoring arguments in empirical language use, runs the risk of accepting at face value such pre-theoretical notions that are in fact open for statistical formulation and interpretation. we believe that the morphological status of chinese morphemes is a matter of degree, subject to approximation with measures on some scale. in the following, we quantify three commonly-accepted properties as computational indices used to describe an affixoid's behavior: (1) morphological productivity, (2) syntactical productivity, and (3) semantic diversity. ## experiments on chinese affixoids in this experiment, we compute the three affixoid indices: morphological productivity, syntactic productivity, and semantic diversity, for each chinese affixoid. these morphemes have been previously defined as prefixes or suffixes in past studies of chinese grammar @xcite . we demonstrate that the three affixoid indices describe and differentiate such morphemes from other affixoids with a generalized additive model. ## conclusion our goal throughout this study has been to empirically revisit a long-standing debate regarding how the status of an affix in chinese may be best defined and ascertained. while free/bound and content/function criteria are often used in linguistic literature on other languages to classify morphemes along a root-affix line, the isolating nature of chinese morphology presents unique challenges. following previous studies, we revised baayen's p index to quantify a morpheme's productivity in a chinese corpus @xcite . measures of syntactic productivity and semantic diversity were also used as indices to investigate a morpheme's status as an affix. the results show that chinese morphemes appear to exist along a root-affix gradient. however, very few of those morphemes sufficiently meet the criteria necessary to justify affix status. finally, diachronic data provides further evidence and a different perspective that lexical polysemy likely plays a role in the development of affixes in mandarin chinese.