Evaluating Multilingual Sentence Embeddings for Translation Error Detection:An English--Greek Contrastive Study
Computation and Language
Summary
The authors studied how well different multilingual sentence embedding models can spot small translation mistakes between English and Greek sentences. They created a test set with various types of errors and checked how the models rated correct versus incorrect translations. They found that one embedding model, BGE-M3, was pretty good but still not as accurate as a specialized quality estimation model called COMETKiwi. The embedding models were better at noticing clear factual or word-level mistakes, while COMETKiwi handled more complex errors like grammar and pronouns better. Overall, the authors suggest that embedding models should be part of bigger systems instead of used alone to evaluate translations.
Authors
Eleftherios Kalogeros, Athanasios Ntalakas, Manolis Gergatsoulis, Paschalis Nikolaou, Sotiria-Lito Alexaki
Abstract
Multilingual sentence embeddings are increasingly used to estimate semantic similarity across languages, yet their sensitivity to fine-grained translation errors remains insufficiently understood. This study investigates whether general-purpose multilingual embedding models can distinguish correct English-Greek translations from minimally modified erroneous alternatives. A contrastive dataset was developed from FLORES+ sentence-aligned reference translations and reviewed by two translation experts. It contains 1,850 examples across ten core and five exploratory error categories, covering factual, lexical-semantic, grammatical, relational, referential, and discourse-level phenomena. Five multilingual sentence-embedding models (BGE-M3, Multilingual E5, Multilingual MPNet, LaBSE, and Jina Embeddings v3) were evaluated using cosine similarity between each English source sentence and its correct and erroneous Greek translations. A reference-free COMETKiwi model was also evaluated as an MT quality-estimation baseline. Performance was assessed through contrastive accuracy and score margins for category-specific sensitivity. BGE-M3 achieved the highest accuracy among embedding models at 89.30 percent, while COMETKiwi achieved 94.49 percent. Embedding models detected explicit factual and lexical changes more reliably than tense-and-aspect and pronoun-coreference errors. COMETKiwi improved performance on several difficult categories, including tense and aspect, pronoun and coreference, and semantic-role errors, but showed lower sensitivity to date-and-time errors and underperformed the embedding models on numbers. The results show complementary error-sensitivity profiles: multilingual sentence embeddings provide useful semantic adequacy signals but are better suited as components of broader translation-evaluation frameworks than as standalone metrics.