Back-translation

A back-translation is a translation of a translated text back into the language it came from, made by someone who has not seen the original. Wikipedia's article defines it in those terms. You then put the back-translation beside the original and look for places where the meaning moved.

Where back-translation is used#

One established use is in medicine. When informed-consent forms and other material for clinical trials are translated, Wikipedia notes, an ethics committee or institutional review board often requires a back-translation.

The idea is the one behind checking a sum by reversing it. Wikipedia's article makes that comparison and adds the limit: words are ambiguous where mathematical symbols are not, so a back-translation is an approximate check and not always a reliable one. Mark Twain made the point at his own expense, by back-translating a French translation of his story The Celebrated Jumping Frog of Calaveras County into English.

What it cannot catch#

A worked example shows the blind spot. A shop's English returns line, "You can return any item within 30 days", is translated into Dutch twice, once with the polite u and once with the familiar je:

• U kunt elk artikel binnen 30 dagen retourneren.
• Je kunt elk artikel binnen 30 dagen retourneren.

Both come back from a careful back-translator as the same English sentence, because English has one word for you. The decision a Dutch reader notices first, how the shop addresses them, is invisible in the check. The same goes for tone, idiom, length on a button and anything else that has no counterpart in the source language. A back-translation also shows wording differences that are not errors, so someone has to sort real changes in meaning from harmless ones.

Back-translation and websites#

For website copy the cost is usually hard to justify: each check takes a second translator, and it still leaves the target language unread by anyone who speaks it. A bilingual reviewer who reads the translation against the source can catch the same changes in meaning, and the register too.

LangRelay does not back-translate. Its Translation grid shows each source line beside its translation for a person to review, and Relay, when you ask it to review a page, reads both and reports changed meaning, such as a different number, price or date or a lost negation, as a major finding, and a line in a different register from the rest of its page as a minor one. By default a translation goes live as soon as it is ready, and free checks hold a page with untranslated text, the wrong language or a changed price. To approve every page yourself, choose Ask me first.

Translation QA covers the wider set of checks a translation goes through, and post-editing website copy covers the review of machine output. For the Dutch register choice in the example, see Dutch website translation.