Helpful or Harmful? The Dual Role of Linguistic Features in LLM-Based Dialectal Machine Translation

Abdelhalim Hafedh Dahou, Mohamed Amine Cheragui


Abstract
Large Language Models (LLMs) have shown promising results in dialectal machine translation, yet the impact of explicit linguistic features remains underexplored. This paper examines whether part-of-speech (POS) tags and diacritization help or hinder LLM-based translation between Algerian dialect (Darija) and Modern Standard Arabic (MSA). Using a linguistically enriched subset of the PADIC dataset, we conduct bidirectional experiments across several frontier and open-weight LLMs, evaluated with automatic metrics and human judgments of adequacy and fluency. Results reveal a dual and asymmetric effect: diacritics can improve adequacy in the MSA → Algerian dialect direction, while POS tags and forced diacritization often introduce noise, especially for Algerian dialect → MSA translation. We further observe a mismatch between traditional overlap-based metrics and human evaluation, suggesting limitations in current evaluation practices. Overall, explicit linguistic augmentation does not consistently benefit LLM-based dialectal translation and must be applied cautiously.
Anthology ID:
2026.osact-1.8
Volume:
The 7th Workshop on Open-Source Arabic Corpora and Processing Tools (OSACT7) with 5 Shared Tasks
Month:
May
Year:
2026
Address:
Palma, Mallorca (Spain)
Editors:
Hend Al-Khalifa, Mo El-Haj, Saad Ezzini
Venues:
OSACT | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
66–75
Language:
External URL:
https://lrec.elra.info/lrec2026-ws-osact-08
DOI:
10.63317/5dpmbr8bbedw
Bibkey:
Cite (ACL):
Abdelhalim Hafedh Dahou and Mohamed Amine Cheragui. 2026. Helpful or Harmful? The Dual Role of Linguistic Features in LLM-Based Dialectal Machine Translation. In The 7th Workshop on Open-Source Arabic Corpora and Processing Tools (OSACT7) with 5 Shared Tasks, pages 66–75, Palma, Mallorca (Spain). Association for Computational Linguistics.
Cite (Informal):
Helpful or Harmful? The Dual Role of Linguistic Features in LLM-Based Dialectal Machine Translation (Dahou & Cheragui, OSACT 2026)
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