Systems and techniques for providing definitions to a user. The provision embodies the context of a text in which the defined term appears. In one aspect, a system includes an electronic device that includes one or more data processing devices programmed to respond to receipt of the user selection of the first term by performing operations. The operations include accessing, from the one or more persistent data storage devices, the characterizations of the contexts of the texts, comparing the accessed characterizations of the contexts of the texts with one or more characteristics of the context of the textual content of a media file, and ranking the definitions of the first term according to respective likelihoods that the definitions appropriately characterize the usage of the first term within the textual content of the media file.