23. A system comprising: one or more processors; memory storing computer-readable instructions, which when executed by the one or more processors, cause the one or more processors to: obtain a corpus of text composed by a user; after obtaining the corpus of text: receive, from the user, input comprising a sequence of symbols of a first symbolic system; determine a plurality of candidate word strings corresponding to the sequence of symbols, each candidate word string of the plurality of candidate word strings comprising two or more words of a second symbolic system, wherein the obtained corpus of text comprises words of the second symbolic system; rank the plurality of candidate word strings based on a probability of occurrence of each candidate word string of the plurality of candidate word strings in the obtained corpus of text; and display, based on the ranking, a portion of the plurality of candidate word strings for selection by the user.
23. A system comprising: one or more processors; memory storing computer-readable instructions, which when executed by the one or more processors, cause the one or more processors to: obtain a corpus of text composed by a user; after obtaining the corpus of text: receive, from the user, input comprising a sequence of symbols of a first symbolic system; determine a plurality of candidate word strings corresponding to the sequence of symbols, each candidate word string of the plurality of candidate word strings comprising two or more words of a second symbolic system, wherein the obtained corpus of text comprises words of the second symbolic system; rank the plurality of candidate word strings based on a probability of occurrence of each candidate word string of the plurality of candidate word strings in the obtained corpus of text; and display, based on the ranking, a portion of the plurality of candidate word strings for selection by the user. 32. The system of claim 23 , wherein: the obtained corpus of text is associated with a first context; the input is associated with an input context; and ranking the plurality of candidate word strings is based on a degree of similarity between the input context and the first context.