A Fine-Grained Linguistic Evaluation of Low-Resource Luxembourgish–English MT

Nils Rehlinger


Abstract
Machine translation (MT) evaluation is central in guiding researchers on how to improve a model’s performance. Current automatic evaluation practices fail to provide reliable insights into the specific translation errors that occur, especially for low-resource languages. This paper introduces the Lux-MT-Test-Suite, enabling a linguistically motivated and fine-grained analysis of Luxembourgish–English (LB-EN) MT based on 896 test items covering 12 linguistic categories and 36 linguistic phenomena. We compare a baseline local LLM (Gemma 3), its fine-tuned counterpart (LuxMT), and a proprietary state-of-the-art LLM (GPT-5) to analyse what local LLMs learn through fine-tuning in a low-resource setting and to assess performance differences between local and proprietary systems. The findings identify specific performance gains through fine-tuning, minor degradations, a difference in translation strategies, performance gaps between local and proprietary models, and remaining challenges.
Anthology ID:
2026.loresmt-1.12
Volume:
Proceedings for the Ninth Workshop on Technologies for Machine Translation of Low Resource Languages (LoResMT 2026)
Month:
March
Year:
2026
Address:
Rabat, Morocco
Editors:
Atul Kr. Ojha, Chao-hong Liu, Ekaterina Vylomova, Flammie Pirinen, Jonathan Washington, Nathaniel Oco, Xiaobing Zhao
Venues:
LoResMT | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
138–150
Language:
URL:
https://aclanthology.org/2026.loresmt-1.12/
DOI:
Bibkey:
Cite (ACL):
Nils Rehlinger. 2026. A Fine-Grained Linguistic Evaluation of Low-Resource Luxembourgish–English MT. In Proceedings for the Ninth Workshop on Technologies for Machine Translation of Low Resource Languages (LoResMT 2026), pages 138–150, Rabat, Morocco. Association for Computational Linguistics.
Cite (Informal):
A Fine-Grained Linguistic Evaluation of Low-Resource Luxembourgish–English MT (Rehlinger, LoResMT 2026)
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PDF:
https://aclanthology.org/2026.loresmt-1.12.pdf