Information Theory and Linguistic Variation: A Study of B razilian and E uropean P ortuguese (2025)

Abstract: We present a general analysis of the lexical and grammatical differences between Brazilian and European Portuguese by applying entropy measures, including Kullback-Leibler divergence and word order entropy, across various linguistic levels. Using a parallel corpus of BP and EP sentences translated from English, we quantified these differences and identified characteristic phenomena underlying the divergences between the two varieties. The highest divergence was observed at the lexical level due to word pairs unique to each variety but also related to grammatical distinctions. Furthermore, the analysis of parts-of-speech (POS), dependency relations, and POS tri-grams provided information concerning distinctive grammatical constructions. Finally, the word order entropy analysis revealed that while most of the syntactic features analysed showed similar patterns across BP and EP, specific word order preferences were still apparent.

## introduction portuguese, a romance language from the indo-european family, is the eighth most spoken language in the world according to @xcite , and the most spoken language in the southern hemisphere. it is the official language of eight countries: angola, brazil, cape verde, equatorial guinea, east timor, guinea-bissau, mozambique, and sao tome and principe. however, it is spoken, as the native language, by more than 99% of the population only in portugal and brazil. according to instituto @xcite , in 2021, portuguese was spoken by around 280 million people. due to its population size and increasing economic importance, the brazilian variety of portuguese has expanded its influence throughout the twentieth and twenty-first centuries. the impact of this variety can be seen, for instance, in the field of natural language processing (nlp), where many tools and language models have been specifically developed for brazilian portuguese (e.g., bertimbau @xcite and albertina 100m ptbr @xcite ). despite portugal's smaller population, the european variety of portuguese has maintained its prestige and significant importance within the lusophone community, especially in the nlp field @xcite . unfortunately, other varieties still lack representativeness, particularly in the nlp field, as described by @xcite . since the colonization period, the portuguese spoken in brazil has evolved differently from european portuguese, influenced by various factors, across multiple linguistic levels, including lexical, grammatical, and phonological. the analysis of these differences have been object of a large variety of linguistic works, and the detection of these varieties is a current topic in the nlp community (e.g., vardial shared task 2023 @xcite ). despite efforts to unify the portuguese varieties (e.g., the orthographic agreement (pinto, 2012)), the emphasis on differences appears to be the main trend on social media, where users from various regions engage in endless discussions about the most correct ways to express themselves. one example is the amount of discussion generated by the bbc article @xcite , in which the linguist fernando venâncio states that in a few decades, brazil will be speaking brazilian, a different language from portuguese. while linguistic papers usually focus on specific linguistic differences, often without employing corpus-based analysis, many nlp works tend to concentrate solely on improving tools for specific applications, giving little attention to the analysis of these differences. therefore, the aim of this paper is to provide a general overview of the lexical and grammatical differences between brazilian and european portuguese, using information theory measures such and parallel corpus. our objective is to quantify these differences and, through qualitative analysis, identify the main lexical and grammatical aspects responsible for the observed variations. moreover, we aim to show how efficient these methods are in the identification of typical lexical and grammatical features of different varieties of the same language. the remainder of the paper is organized as follows. in section 2 we discuss related work on brazilian and european varieties of portuguese. sections 3 and 4 presents our methods and results. we conclude with a summary and outlook (section 5). ## related work as previously mentioned, purely linguistic works comparing european and brazilian portuguese tend to focus on specific linguistic phenomena. for example, the work by kato and @xcite describes what the authors refer to as a major difference in the grammar of the two varieties, namely the placement of clitic pronouns. moreover, they also propose an analysis concerning information focus, as well as contrastive and emphatic focus. the difference between wh-questions in both varieties was examined diachronically by de paula (2017), revealing a clear temporal evolution with notable differences in word order patterns (e.g., whv versus whsv). an interesting study regarding the lexical level was conducted by @xcite . the authors compared brazilian and european portuguese at the lexical level using uniformity measures developed by @xcite . they focused on the lexical fields of clothing and soccer, identifying a divergence only in the clothing category. the authors examined 21 pairs of synonyms to calculate the uniformity measures. in contrast, our approach is broader, as our measures allow us to identify divergent terms without relying on a pre-established list and can also be used to identify typical grammatical patterns in each variety. many other studies focused on intonational and phonological aspects (cf. @xcite ; @xcite ; @xcite ), which are not the focus of our analysis. the focus of nlp studies on portuguese varieties is typically on detecting the correct variety, as seen in the 2023 and 2024 vardial shared tasks @xcite . besides specific shared tasks organized for this purpose, variety detection is also the subject of other studies, such as the system proposed by @xcite , which focuses on tweets from both varieties and achieves an accuracy of 0.93. another valuable application of nlp tools for different varieties of portuguese was presented by @xcite . the authors focused on the localization task (i.e., adapting linguistic and cultural material between different locales). using large language models, they achieved considerable success in adapting machine translation to brazilian and european portuguese. regarding the use of information theory to describe language variation, @xcite presented a data-driven diachronic analysis of scientific english, detecting periods of linguistic change in terms of lexical and grammatical features. their approach is based on relative entropy @xcite , comparing temporally adjacent periods and sliding along the timeline from past to present. in this paper, our aim is to adopt a similar approach; however, instead of conducting a diachronic analysis, we propose to compare different varieties of portuguese synchronically. entropy measures are also relevant for comparing different languages in terms of word order patterns. in typology, @xcite used entropy in quantitative studies of word order variation, measuring it at different levels of granularity. additionally, @xcite applied entropy measures to demonstrate that the impact of word order on language structure is a statistical linguistic universal. however, these typological studies do not address potential changes in word order across different varieties of the same language. thus, our approach aims to use word order entropy measures to detect syntactic variation between european and brazilian portuguese, to assess whether these differences should be considered in typological studies involving portuguese. ## conclusion and future work in this paper, we provided a general overview of the lexical and grammatical differences between brazilian and european portuguese. by applying entropy measures (i.e., kullback-leibler divergence and word order entropy) across various linguistic levels to a parallel corpus of bp and ep sentences translated from english, we quantified these differences and identified the most characteristic phenomena underlying these divergences. regarding kld, the highest divergence was observed at the lexical level. the lexical analysis not only allowed us to identify word pairs that differ between the two varieties but also revealed specific grammatical preferences, such as the loss of the pro-drop phenomenon in bp. additionally, the analysis of pos, dependency relations, and pos tri-grams enabled a more detailed examination of the grammatical constructions typical to each variety (e.g., the use of the gerund and the position of clitic objects). finally, the word order entropy study showed that, while the majority of the 18 features analyzed exhibited similar results, specific word order preferences were still observed between the varieties. for future work, we aim to expand this analysis using larger corpora to verify whether the tendencies identified in this study (e.g., the order of clausal subject and predicate) can be confirmed. additionally, as the methods used here can be applied to studies of linguistic variation in general, we plan to extend this analysis to other varieties of portuguese. we also intend to complement our study with other information-theoretic measures, such as surprisal to help us identify what would be the most unexpected words and grammatical constructions in each variety when processed with a model trained with a different one.