Nouns through the Ages.,Analysing Latin Morphological Productivity with Lemlat
Authors: Marco Budassi, Eleonora Litta, Marco Carlo Passarotti (Università di Pavia, Università Cattolica del Sacro Cuore, 2017)
Topic: Latin Resources

Abstract
This paper aims at examining the diachronic distribution of one of the richest classes of nouns in Latin, namely those ending in \mbox{-io}. The work is performed through the combined use of a morphological analyser for Latin (Lemlat), and a database collecting all word forms occurring through different periods of Latin language (TF-CILF).

Introduction
The investigation of lexical data of Classical languages through the use of linguistic resources and Natural Language Processing (NLP) tools has witnessed a surge of interest in the past decade. As far as Latin is concerned, today several textual and lexical resources, as well as NLP tools, are being used in lexicographic research., AUTHOR, AUTHOR and AUTHOR.} One of the bedrocks of this type of research is the use of morphological analysers, that is, tools that, given an input word form, output its corresponding lemma(s) and morphological features. First released at the beginning of the 1990s and recently made freely available in its version 3.0 AUTHOR, Lemlat is one of the best performing morphological analysers and lemmatisers for Latin.. See AUTHOR for a comparative evaluation of the morphological analysers currently available for Latin. Lemlat is currently in the process of being enriched with all lemmas contained in the glossary of Medieval Latin Glossarium mediae et infimae latinitatis compiled by Charles Du Cange et alii in 1883-1887 AUTHOR. One of the first groups of lemmas from Du Cange which was included into the lexical basis of Lemlat was that collecting all 3\textsuperscript{rd} declension nouns ending in \mbox{-io}, one of the most productive affixes in all periods of Latin, up to Romance languages AUTHOR. The aim of this study is to perform a diachronic quantitative evaluation of 3\textsuperscript{rd} declension nouns ending in \mbox{-io}. To do so, first we use Lemlat to lemmatise all word forms of such nouns contained in Thesaurus formarum totius latinitatis a Plauto usque ad saeculum XXum (TF-CILF) AUTHOR. Then we evaluate the results of the lemmatisation in both quantitative and qualitative terms.

Conclusion
In this paper, we presented a study of the diachronic distribution of Latin nouns ending in \mbox{-io} by processing word forms from the TF-CILF corpus with the morphological analyser Lemlat. We demonstrated that the \mbox{-io} suffix is very productive across all periods of Latin language, showing a particularly high frequency in both Medieval and Neo-Latin texts. Ratio remains always the most used \mbox{-io} noun across the entire diachronic span covered by the corpus used in our work. One step further in the study of \mbox{-io} nouns would be to establish derivational relationships for each lemma and to verify which of the two lexical groups (Lemlat or Du Cange) the input lemma belongs to. Also, an evaluation of the unknown word forms after the lemmatisation process should be performed. Given the wide lexical coverage provided by Lemlat, our work represents a positive example of how much NLP tools can help to investigate diachronic aspects of language. %However, if this holds true when dealing with basic levels of linguistic analysis (like lemmatisation and PoS tagging), things become trickier when syntactic parsing is concerned. In this respect, Ponti and Passarotti (2016) show the dramatic drop of the accuracy rates of a dependency parser trained on a Medieval Latin treebank when applied to Classical Latin texts. The wide diachronic as well as diatopic span over which Latin texts are spread opens an appealing challenge for research in NLP, which has to address the problem of portability of NLP tools across time, place and genre. In this sense, Latin texts represent a perfect dataset both for developing and for evaluating techniques of domain-adaptation of NLP tools.