SMOL: Professionally translated parallel data for 115 under-represented languages
Isaac Caswell, Elizabeth Nielsen, Jiaming Luo, Colin Cherry, Geza Kovacs, Hadar Shemtov, Partha Talukdar, Dinesh Tewari, Baba Mamadi Diane, Djibrila Diane, Solo Farabado Cissé, Koulako Moussa Doumbouya, Edoardo Ferrante, Alessandro Guasoni, Christopher Homan, Mamadou K. Keita, Sudhamoy DebBarma, Ali Kuzhuget, David Anugraha, Muhammad Ravi Shulthan Habibi, Genta Indra Winata, Anthony Munthali, Sina Ahmadi, Andrei Chemyshev, Mingfei Lau, Jonathan Eng
TL;DR
This work introduces SMOL, a professionally translated parallel data suite aimed at enabling machine translation for 124 low-resource languages through two complementary datasets, SmolSent (sentence-level, token-coverage focused) and SmolDoc (document-level, topic-diverse). It details English-centered data selection, including a token-set-cover approach and a prompt-based document generation method, augmented by human-in-the-loop curation and factuality annotations. Finetuning and prompting experiments with Gemini 2.0 demonstrate substantial ChrF improvements across language pairs, with the strongest gains when combining SmolSent, SmolDoc, and Gatitos for diverse, non-English-centric languages. The dataset is openly released to support researchers and practitioners, though limitations such as potential English-source bias and multi-way data overfitting are acknowledged, guiding future work toward broader language coverage and robust evaluation.
Abstract
We open-source SMOL (Set of Maximal Overall Leverage), a suite of training data to unlock machine translation for low-resource languages. SMOL has been translated into 124 (and growing) under-resourced languages (125 language pairs), including many for which there exist no previous public resources, for a total of 6.1M translated tokens. SMOL comprises two sub-datasets, each carefully chosen for maximum impact given its size: SMOLSENT, a set of sentences chosen for broad unique token coverage, and SMOLDOC, a document-level resource focusing on a broad topic coverage. They join the already released GATITOS for a trifecta of paragraph, sentence, and token-level content. We demonstrate that using SMOL to prompt or fine-tune Large Language Models yields robust chrF improvements. In addition to translation, we provide factuality ratings and rationales for all documents in SMOLDOC, yielding the first factuality datasets for most of these languages.
