TurEngMix: A Text Corpus and Benchmark for Turkish-English Code-Mixed Language Identification and Named Entity Recognition

Ilayda Dogan, Phuong-Anh Nguyen-Le, Julia Mendelsohn


Abstract
Natural language processing systems underperform on code-mixed text, particularly for low-resource language pairs. Turkish-English poses a further challenge: it lets English stems combine with Turkish suffixes to form single mixed-language tokens. We introduce TurEngMix, a corpus of 5.5K noisy, naturally occurring social media posts (486,974 tokens) rich in Turkish-English code-mixing. From this corpus, we construct a new Turkish-English benchmark for code-mixed language identification (LID) and named entity recognition (NER), comprising 15K expert-annotated tokens. Evaluating both decoder LLM and fine-tuned encoder baselines, we find that monolingual Turkish and English tokens are labeled reliably, but all models have high error rates on mixed-language tokens for both LID and NER. For morphologically integrated tokens, NER error rates were 5.2× and 6.3× higher for GPT-4o and Qwen, respectively. This highlights how morphological integration remains a challenge. We release the corpus, annotations, and code to support future computational and sociolinguistic research on Turkish-English code-mixing.
Anthology ID:
2026.wnut-1.24
Volume:
Proceedings of the 11th Workshop on Natural User-generated Text
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
JinYeong Bak, Rob van der Goot, Hyeju Jang, Weerayut Buaphet, Alan Ramponi, Wei Xu, Alan Ritter
Venues:
WNUT | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
341–355
Language:
URL:
https://aclanthology.org/2026.wnut-1.24/
DOI:
Bibkey:
Cite (ACL):
Ilayda Dogan, Phuong-Anh Nguyen-Le, and Julia Mendelsohn. 2026. TurEngMix: A Text Corpus and Benchmark for Turkish-English Code-Mixed Language Identification and Named Entity Recognition. In Proceedings of the 11th Workshop on Natural User-generated Text, pages 341–355, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
TurEngMix: A Text Corpus and Benchmark for Turkish-English Code-Mixed Language Identification and Named Entity Recognition (Dogan et al., WNUT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.wnut-1.24.pdf