Adaptation is a form of translation that takes advantage of similarities in related languages to speed the translation process. Adaptation minimizes the need for exegesis.
Translation is a general term for transforming text from one language to another. Generally two languages are involved—the original language and the target language. Involved in the translation process is making sure that the original language meaning is maintained in the translation. Exegesis is the process of validating that meaning.
Adaptation is "translating a translation." In this case there are three languages involved:
The original language of the text, (sometimes this language is used for glossing.)
A source language, which already contains a translation and exegesis of the original
The target language for the new translation. The target language must be closely related to the source language. The exegesis in the target language depends on that of the source language.
Adaptation translates from the source language to the target language. This process requires that the source language translation is exegetically correct. Since the source language and the target language are highly related most of the exegesis is automatically maintained. In cases where the original meaning would not be maintained, the translator must retranslate the text into the new language.
Adapt It Concepts Overview
How adaptation is done
Adaptation versus retranslation