Dictionaries to the Rescue: Cross-Lingual Vocabulary Transfer for Low-Resource Languages Using Bilingual Dictionaries

Fuente: arXiv
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Autores principales: Sakajo, Haruki, Ide, Yusuke, Vasselli, Justin, Sakai, Yusuke, Tian, Yingtao, Kamigaito, Hidetaka, Watanabe, Taro
Formato: Preprint
Publicado: 2025
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author Sakajo, Haruki
Ide, Yusuke
Vasselli, Justin
Sakai, Yusuke
Tian, Yingtao
Kamigaito, Hidetaka
Watanabe, Taro
author_facet Sakajo, Haruki
Ide, Yusuke
Vasselli, Justin
Sakai, Yusuke
Tian, Yingtao
Kamigaito, Hidetaka
Watanabe, Taro
contents Cross-lingual vocabulary transfer plays a promising role in adapting pre-trained language models to new languages, including low-resource languages. Existing approaches that utilize monolingual or parallel corpora face challenges when applied to languages with limited resources. In this work, we propose a simple yet effective vocabulary transfer method that utilizes bilingual dictionaries, which are available for many languages, thanks to descriptive linguists. Our proposed method leverages a property of BPE tokenizers where removing a subword from the vocabulary causes a fallback to shorter subwords. The embeddings of target subwords are estimated iteratively by progressively removing them from the tokenizer. The experimental results show that our approach outperforms existing methods for low-resource languages, demonstrating the effectiveness of a dictionary-based approach for cross-lingual vocabulary transfer.
format Preprint
id arxiv_https___arxiv_org_abs_2506_01535
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Dictionaries to the Rescue: Cross-Lingual Vocabulary Transfer for Low-Resource Languages Using Bilingual Dictionaries
Sakajo, Haruki
Ide, Yusuke
Vasselli, Justin
Sakai, Yusuke
Tian, Yingtao
Kamigaito, Hidetaka
Watanabe, Taro
Computation and Language
Artificial Intelligence
Cross-lingual vocabulary transfer plays a promising role in adapting pre-trained language models to new languages, including low-resource languages. Existing approaches that utilize monolingual or parallel corpora face challenges when applied to languages with limited resources. In this work, we propose a simple yet effective vocabulary transfer method that utilizes bilingual dictionaries, which are available for many languages, thanks to descriptive linguists. Our proposed method leverages a property of BPE tokenizers where removing a subword from the vocabulary causes a fallback to shorter subwords. The embeddings of target subwords are estimated iteratively by progressively removing them from the tokenizer. The experimental results show that our approach outperforms existing methods for low-resource languages, demonstrating the effectiveness of a dictionary-based approach for cross-lingual vocabulary transfer.
title Dictionaries to the Rescue: Cross-Lingual Vocabulary Transfer for Low-Resource Languages Using Bilingual Dictionaries
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2506.01535