1. A method performed by a data processing apparatus, the method comprising: receiving data identifying source language text; receiving a translation for the source language text from a machine translation system, the translation including translated text corresponding to the source language text and segmentation data for the translated text, wherein the segmentation data includes a first segmentation of the translated text, the first segmentation dividing the translated text into two or more segments receiving one or more alternative translations for each of the two or more segments of the first segmentation; and sending executable instructions that, when executed by a user device, cause the user device to perform operations comprising: presenting the source language text and the translated text in a user interface; and in response to a user selection of a first portion of the translated text, presenting in the user interface one or more alternative translations for a first segment to which the first portion of the translated text corresponds according to the first segmentation.