LatInfLexi: an Inflected Lexicon of Latin Verbs
Authors: Matteo Pellegrini, Marco Carlo Passarotti (Università di Bergamo, Università Cattolica del Sacro Cuore, 2018)
Topic: Lexical and Semantic Resources and Analysis

Abstract
We present a paradigm-based inEnglish. We present a paradigm-based inflected lexicon of Latin verbs built to provide empirical evidence supporting an entropybased estimation of the degree of uncertainty in inflectional paradigms. The lexicon contains information on the inflected forms that occupy the 254 morphologically possible paradigm cells of 3,348 verbal lexemes extracted from a frequency lexicon of Latin. The resource also includes annotation of vowel length and the frequency of each form in different epochs.

Introduction
In this paper, we describe the construction of LatInfLexi, an inflected lexicon of Latin verbs organized in lexemes1 and paradigm cells. In morphological theory, there is a recent trend towards a more realistic modelling of complex inflectional systems: for instance, Ackerman et al. (2009) and Bonami and Boyé (2014) propose that the analysis should take a full inflected form as a starting point, without assuming any segmentation a priori. In such approaches, what is investigated is not the construction of forms from smaller units like stems and inflectional endings, but rather their predictability given knowledge of other forms. This can be done by using the information theoretic notion of conditional entropy to estimate the uncertainty in guessing the content of the paradigm cell of a lexeme knowing another inflected form of the same lexeme, by weighting the probability of application of each inflectional pattern based on their type frequency in real data. To do so, large-scale inflected lexicons listing all forms of a representative selection of lexemes are needed. Such resources are increasingly being developed for modern languages – see among else Zanchetta and Baroni (2005) and Calderone et al. (2017) for Italian, Neme (2013) for Arabic, Bonami et al. (2014) and Hathout et al. (2014) for French. However, to the best of our knowledge, there are no resources of this kind for Latin, although their (semi-)automatic building is made possible by the current availability of several morphological analyzers for Latin, including Words (http://archives.nd.edu/words.html), Lemlat (www.lemlat3.eu), Morpheus (https://github.com/tmallon/morpheus), the PROIEL Latin morphology system (https://github.com/mlj/proiel-webapp/tree/master/lib/morphology) and LatMor (http://cistern.cis.lmu.de). Our resource was created to fill this gap and to enable a quantitative, entropy-based analysis of Latin verb inflection.

Conclusion
We described the design and building of a lexeme-based inflected lexicon consisting of 850,392 paradigm cells of 3,348 Latin verbs. Our first objective in the near future is to make the resource complete in terms of lexical coverage, including the lexemes of the other PoS. The lexicon is available for download as a .csv file at https://github.com/matteopellegrini/LatInfLexi. We also plan to include phonetic annotation, by giving the IPA transcription of each form, which can be obtained semi-automatically by applying a script provided by the Classical Language Toolkit (Johnson et al., 2014-17) to stems and endings. Another welcome addition would be to account for cases of overabundance, by allowing more than one form to appear in the same paradigm cell. However, to decide which cell-mates to keep and which ones to discard, their frequency in Latin texts should be preliminarily evaluated. In this respect, it has to be noted that the frequencies in the TFTL refer to bare surface forms, with no contextual disambiguation. For instance, the frequency of veniam comprises not only occurrences of both the PRS.ACT.SBJV.1SG and FUT.ACT.IND.1SG of the verb venio ‘to come’, but also of the ACC.SG of the noun venia ‘indulgence’. To get an idea of the impact of morphological ambiguity on our lexicon, we analyzed all the generated forms with Lemlat (version 3.0). We found that only for about 23% (170,735) of the 752,537 forms Lemlat outputs only one analysis (i.e. one lemma and one set of morphological features), the remaining 581,802 (about 77%) being ambiguous. This result weakens the reliability of the frequency data provided in the lexicon. Therefore, disambiguation is needed, although this would require a very time-consuming work. However, to tackle the problem of ambiguity, a first useful step is distinguishing between cases like veniam above, which can be analyzed as an inflected form of two different lemmas, and cases where the different analyses only refer to different forms of the same lemma, e.g. laudatis, that appears both in the PRS.ACT.IND.2PL and in the PRF.PTCP.DAT/ABL.PL of laudo ‘to praise’, but cannot be a form of other lemmas. We call these different types ‘exolemmatic’ and ‘endolemmatic’ ambiguity, respectively (cf. Passarotti and Ruffolo, 2004). Cases of exolemmatic ambiguity are clearly more problematic, but they are also much rarer: only 79,490 (about 10%) of the forms in our resource belong to this type. The great majority of ambiguous forms only give rise to endolemmatic ambiguity, as can be observed in Table 4 below, where the relevant data are summarized. As far as endolemmatic ambiguity is concerned, although its quantitative impact is far greater, it could be considerably reduced in a principled manner. Indeed, it should be noted that in many cases this kind of ambiguity is due to systematic syncretism. For instance, the cells FUT.ACT.IMP.2SG and FUT.ACT.IMP.3SG are never unambiguously analyzed, because they are always identical for a same verb. Given the full systematicity of this syncretism, which holds for all lexemes, these cells could be considered as only one from a purely morphological point of view. Therefore, the problem of endolemmatic ambiguity could be at least reduced by adopting an approach based on “morphomic paradigms” (Boyé and Schalchli, 2016), where always syncretic cells are conflated, rather than on morphosyntactic paradigms. This would be helpful especially in nominal forms like participles and gerundives, where such cases of systematic syncretism are widespread. When such ambiguity issues will have been resolved, it will also be possible to exploit the frequency data in a more systematic fashion, e.g. to perform diachronic investigations on how the frequency of specific (groups of) forms or paradigm cells change across the four considered epochs, or to model Latin inflectional morphology in an even more realistic way, by considering also the token frequency of inflected forms, as has been recently proposed by Boyé (2016).