How Well Do Language Models Handle Romanian Diacritics? A Comparison of Monolingual and Multilingual Architectures

Alexandra Toma, Maria Cristina Popescu


Abstract
Romanian orthography relies on five diacritic characters (ă, î, â, ş, ţ) that are frequently omitted in informal digital text, yet the impact of text cleaning decisions regarding diacritics on Romanian language models has not been systematically studied across architectures and tasks. We address this gap by examining how diacritics affect subword tokenization, contextual embeddings, and three downstream tasks - POS tagging, named entity recognition, and semantic textual similarity - comparing Romanian BERT with mBERT, DistilmBERT, and mT5. Each model is fine-tuned on diacriticpreserving and diacritic-stripped data and evaluated on both, isolating both overall performance and robustness to train–test mismatch. This work provides the first systematic, multitask account of how diacritic effects propagate from tokenization to downstream performance, showing this depends jointly on pretraining corpus and architecture, and offers practical guidance for Romanian NLP systems that must handle diacritic-inconsistent text.
Anthology ID:
2026.oracle-main.15
Volume:
The Proceedings of the Workshop on Open Reasoning Across Cultures Languages (ORACLE)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Leonardo Ranaldi, Giulia Pucci, Federico Ranaldi, Marco Valentino, Alexandra Birch, Fabio Massimo Zanzotto
Venues:
ORACLE | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
234–245
Language:
URL:
https://aclanthology.org/2026.oracle-main.15/
DOI:
Bibkey:
Cite (ACL):
Alexandra Toma and Maria Cristina Popescu. 2026. How Well Do Language Models Handle Romanian Diacritics? A Comparison of Monolingual and Multilingual Architectures. In The Proceedings of the Workshop on Open Reasoning Across Cultures Languages (ORACLE), pages 234–245, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
How Well Do Language Models Handle Romanian Diacritics? A Comparison of Monolingual and Multilingual Architectures (Toma & Popescu, ORACLE 2026)
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PDF:
https://aclanthology.org/2026.oracle-main.15.pdf