Machine translation (MT) models typically return one single translation for each input segment. This means that when the input segment is ambiguous, the model must choose a translation among various valid options without regard to the intended use case or target audience.

Specific problems can arise for spoken language translation from English into languages that have multiple levels of formality expressed through honorifics or “grammatical register”. For example, the sentence ‘Are you tired?’ can be translated in German as ‘Sind Sie müde?’ in the formal register and as ‘Bist du müde?’ in the informal one. For applications of spoken language translation, leaving the model to choose between different valid translation options can lead to translations that are inconsistent or use an inappropriate formality level, which can be perceived as rude or jarring for speakers from certain cultures and for certain use cases (e.g. customer support chat).

How formality distinctions are expressed grammatically and lexically can vary widely by language. In many Indo-European languages (e.g., German, French, or Russian), the formal and informal registers are distinguished by the second person pronouns and/or verb agreement. In other languages like Korean, distinctions that express polite, respectful, and humble speech can be more extensive: morphological markings on the main verb, as well as on some nouns and adjectives, specific lexical choices and longer sentences. Languages might also vary stylistically from one variety to another (e.g. Portugal Portuguese and Brazilian Portuguese). Still, other languages like Vietnamese present challenges in terms of resources available.

Last year’s results confirmed that zero-shot settings and languages with many grammatical and lexical formality distinctions are challenging settings for controlling formality. This year’s special task invites participants to advance research in effective methods for bridging the gap in formality control for zero-shot cases and for languages with rich grammatical and lexical formality distinctions. For this year, we focus on Korean and Vietnamese in the supervised setting and Portugal Portuguese (to explore potential transfer between regional varieties) and Russian in the zero-shot setting.


Accessing the data

The annotated formality training data is now available for download under the CDLA-Sharing-1.0 License at this location: amazon-science/IWSLT2023.

Language pairs

For the formality control task, we propose supervised and zero-shot settings focusing on text-to-text translation of spoken language.

The following language pairs will be evaluated in the supervised setting (formality-annotated training data and test data will be released):

  1. English → Korean (EN-KO)
  2. English → Vietnamese (EN-VI)

In addition, we will release test data only for the following language pairs in the zero-shot setting:

  1. English → Portugal Portuguese (EN-PT)
  2. English → Russian (EN-RU)

Formality-annotated data

As part of this special task, we will release novel targeted train and test sets comprising of source segments paired with two contrastive reference translations, one for each formality level (informal and formal). Formality distinctions are expressed by the use of grammatical register or honorific language. Table 1 gives examples of annotated contrastive translations from the dataset and Table 2 reports the number of source segments used for training and evaluation.

Table 1 Contrastive reference translations with different formality levels. Phrase-level formality markers in the target languages are annotated with [F]text[/F].

Language   Text
KO Source Yeah Did your mom know you were throwing the party?
  Informal 그, 어머님은 [F]네가[/F] 그 파티 연 거 [F]아셔[/F]?
  Formal 그, 어머님은 [F]님이[/F] 그 파티 연 거 [F]아세요[/F]?
VI Source Is the sun blocking your internet signal tonight?
  Informal Tối nay mặt trời có chặn tín hiệu internet của [F]bạn[/F] không?
  Formal Tối nay mặt trời có chặn tín hiệu internet của [F]quý vị[/F] không [F]ạ[/F]?

Table 2. Number of source segments in the released dataset.

setting language pair train test
supervised EN-KO 400 600
supervised EN-VI 400 600
zero-shot EN-PT 0 600
zero-shot EN-RU 0 600

This special task will offer two training scenarios: supervised and zero-shot. For the supervised training scenario, participants can use the labeled training set for training and development. For the zero-shot task, we will release only test data.


Participants can build systems for evaluation under the following settings:

Note: in all cases, no additionally manually created formality-labeled data is allowed. However, for the unconstrained setting, obtaining additional annotations automatically is allowed as long as the code and data will be shared.


We will provide baselines for the constrained supervised task based on the transfer learning approach detailed in Nadejde et al., 2022, where a generic pre-trained neural machine translation model (trained on CCMatrix) is finetuned on generic unlabelled and formality-annotated contrastive controlled datasets. Please refer to the original paper for more details.


Details TBA.


We will evaluate the submitted system outputs along the following two dimensions:

a) The overall translation quality of the outputs will be evaluated using SacreBLEU v2.0.0, and COMET (eamt22-cometinho-da) on both the shared task-provided test sets and a generic test set. We will use FLORES as our generic quality test bed for all language pairs under supervised and zero-shot settings.

b) Formality control of the models will be evaluated using:

  1. Matched-Accuracy (M-Acc), a reference-based corpus-level automatic metric that leverages phrase-level formality markers from the references to classify a system-generated hypothesis as formal, informal, or neutral. The final corpus-level score is the percentage of system outputs that matches the desired formality level.

  2. a reference-free variant of M-Acc that uses a multilingual formality classifier to label a system-generated hypothesis as formal or informal. The final corpus-level score is the percentage of system outputs that matches the desired formality level. The formality classifier will be released soon.

Details on the deciding criteria for the overall ranking of the submitted systems will be updated soon.


  • Sweta Agrawal (UMD)
  • Marine Carpuat (UMD)
  • Elijah Rippeth (UMD)
  • Anna Currey (AWS AI Labs)
  • Benjamin Hsu (AWS AI Labs)
  • Phu Mon Htut (AWS AI Labs)
  • Maria Nadejde (AWS AI Labs)
  • Xing Niu (AWS AI Labs)


Chairs: Benjamin Hsu, AWS AI Labs and Marine Carpuat, UMD