E vo S em: A database of polysemous cognate sets (2023)

Abstract: Polysemies, or “colexifications”, are of great interest in cognitive and historical linguistics, since meanings that are frequently expressed by the same lexeme are likely to be conceptually similar, and lie along a common pathway of semantic change. We argue that these types of inferences can be more reliably drawn from polysemies of cognate sets (which we call “dialexifications”) than from polysemies of lexemes. After giving a precise definition of dialexification, we introduce Evosem, a cross-linguistic database of etymologies scraped from several online sources. Based on this database, we measure for each pair of senses how many cognate sets include them both — i.e. how often this pair of senses is “dialexified”. This allows us to construct a weighted dialexification graph for any set of senses, indicating the conceptual and historical closeness of each pair. We also present an online interface for browsing our database, including graphs and interactive tables. We then discuss potential applications to NLP tasks and to linguistic research.

## introduction colexification is the structural pattern whereby two meanings are expressed by the same word in a given language: e.g., spanish pueblo colexifies the meanings people and village. while polysemy is defined semasiologically, as a property of a word, colexification is defined onomasiologically, as a property of a pair of meanings. these are two sides of the same coin: if a pair of meanings is colexified, then this means they are senses of the same polysemous word. the concept of colexification was introduced by @xcite in the context of lexical typology, with the aim of discovering universal patterns of conceptual structure, adapting the semantic-map approach that had already proven fruitful in typological studies of grammar @xcite . since then, a number of works have been published on the topic of colexification. some of these suggest additional sources of data (e.g. @xcite , while others look for universals in lexical semantics (e.g. @xcite , or try to predict patterns of colexification from properties of the meanings themselves (e.g. @xcite @xcite . the growing body of research into colexification has also led to the creation of the clics database @xcite , available at https: //clics.clld.org ), now in its third edition: the empirical dataset that it provides makes it possible to test hypotheses about cross-linguistic patterns of colexification. this in turn has led to recent applications in the field of nlp, with presentations at major venues such as @xcite (gwc2021) who question the universality of common colexifications by comparing different colexification databases, @xcite who use colexification to create cross-lingual resources and @xcite who infuse language embeddings with semantic typology using colexification information. while it yields some insight into universal constraints on semantic change, "strict colexification" @xcite , defined in terms of synchronic properties of lexemes, misses the semantic links that are synchronically absent, yet can be revealed by studies of etymology. incorporating semantic change into the study of lexical typology would contribute to a growing body of research on computational approaches in this domain (e.g. @xcite . this issue is addressed by the new concept of dialexification @xcite , the structural pattern whereby two meanings are expressed by members of the same cognate set. for example, knowledge of regular sound change in the indo-european family shows that norwe-gian gård 'land', gothic gards 'house' and polish gród 'city' are all cognate, since they all descend from the same proto-indo-european (p-ie) etymon *g h órd h os @xcite . the historical relations that link these three concepts cannot be captured by the notion of colexification, since none of these words has more than one of these meanings; but they can be described as instances of dialexification. more specifically, we can say that the semantic pairs {land-house}, {land-city}, and {house-city} are dialexified by (or under) the p-ie form *g h órd h os. if two meanings a and b are dialexified, this means that either a evolved into b, b evolved into a, or both a and b evolved from a common source. in other words, dialexification is always indicative of a historical relation between two meaningsone that may not have been captured by earlier conceptual tools. in this paper, we present evosem, a database and a website ( http://tiny.cc/evosem ) dedicated to the study of dialexification. it consists of etymologies and definitions scraped from the englishlanguage wiktionary ( https://en.wiktionary. org ), itself a compilation of earlier scholarly work from various sources; as well as the austronesian comparative dictionary or acd @xcite and the sino-tibetan etymological dictionary and thesaurus or stedt @xcite . among other features, evosem allows us to measure how often any given pair of meanings is dialexified across the world's languages. this paper is organized as follows. section 2 will define the notion of dialexification mathematically, and contrast it with colexification. section 3 will describe the process of data collection and postprocessing. section 4 will discuss the visualization of the data on our companion website. finally, section 5 will discuss potential applications of evosem to nlp tasks and to linguistic research. ## definitions let @xmath0, . . . , l n } be a set of languages. for each language @xmath1, we have a vocabulary v @xmath2, . . . , w |v l | } of words and/or morphemes. let c(w) be the set of meanings (also called concepts or glosses) of the word @xmath3. furthermore, let @xmath4. we say that w is a reflex of e, and we call the set of all reflexes of e the cognate set to which w belongs. two concepts c i and c j are said to be "dialexified"-which we represent as "δ(c i , c j )"-if there exist two words w p and w q such that w p expresses c i , w q expresses c j , and w p and w q are cognate (i.e., have the same etymon). mathematically, dialexification is a symmetric and reflexive relation that can be formally defined as follows: as for colexification, it corresponds to the situation where w p and w q are the same; in this case, w p and w q are obviously cognate, since they necessarily descend from the same etymon. we write the colexification relation as κ(c i , c j ), and define it as follows: like dialexification, this relation is symmetric and reflexive. also, κ(c i , c j ) ⇒ δ(c i , c j ) for all c i and c j : in other words, any relation of colexification is also a relation of dialexification, though the converse is not true. note that the etymon of a given word is not always attested: it may be a proto-form reconstructed using the comparative method @xcite . its exact form may thus be uncertain; but this does not affect our ability to identify cases of dialexification, since all that matters for the definition is whether two words have the same etymon, i.e. belong to the same cognate set. to put it another way, the domain of dialexification is not, strictly speaking, the etymon itself, but rather the cognate set that descends from the etymon. thus, to say that a given etymon dialexifies concepts a and b is not a direct claim about the semantics of the original etymon: it is simply a statement about the meanings of its descendants. strictly speaking, we could have defined dialexification in terms of cognate sets. but since it is more convenient to refer to a cognate set by its etymon than to list out all the cognate forms (and since there is a one-to-one correspondence between etyma and the cognate sets that descend from them), we prefer the etymon-based definition. we make a distinction between a root, which is the minimal unit of historical reconstruction (e.g. p-ie *g h erd h -'enclose'), and an etymon, i.e. a proto-form that is morphologically derived from a root: e.g., the nouns *g h órd h -os and *g h r . d h -ós (both glossed 'enclosure') are two distinct etyma derived from the root *g h erd h -. strictly defined, relationships of dialexification are always assessed at the level of the etymon rather than its root. 1 note that "cognate sets", as we define them in this paper, include not only direct descendants of etyma, but also borrowings. for example, the cognate set that descends from p-ie *g h órd h os includes not only russian gorod 'city', but also yakut (turkic) kuorat 'city', which is borrowed from the russian word. this differs from the way cognate sets are usually defined in historical linguistics (i.e. excluding borrowings); however, we see no principled reason to distinguish between semantic changes that affect borrowed forms and those that affect inherited forms, and so this distinction is not relevant for defining dialexification. regardless, we retain information about the borrowed status of lexemes in our database, to allow for future analyses that are sensitive to this distinction. ## data collection we now describe how we went about assembling the evosem dataset. ## visualization in this section, we present the tools provided on the evosem website for exploring the database. ## applications evosem allows us to observe historical connections between meanings that would be missed if we were to limit ourselves to looking at colexifications. for example, the meanings chest and stomach are dialexified 6 times in our data, but are not colexified even once. such instances of pure dialexification are useful to historical linguists, as they help to more accurately determine whether two forms with different meanings are potential cognates. they also provide insight into pathways of semantic change. thus, while the pair {chest-stomach} is dialexified δ = 6 times, {chest-heart} has δ = 13, and {heart-stomach} has δ = 11. from this, one can hypothesize that, if a form that once meant 'chest' later came to mean 'stomach', at some intermediate point it probably included 'heart' among its meanings. finally, dialexifications provide a way of measuring the similarities between concepts-much like colexifications, but in a manner that controls for shared descent. this opens up the possibility of using dialexifications to improve performance in similarity judgment tasks (as in @xcite , or to bootstrap the inference of semantic features in cross-lingual datasets (as in @xcite .