27. The system of claim 25 , where the variation of context in which the sequence occurs is calculated as a measure of entropy of the context of the sequence.
25. A device comprising: a memory to store instructions; and a processor to execute the instructions to implement: means for receiving a sequence of terms; means for calculating a first value representing a coherence of terms in the sequence of terms; means for calculating a second value representing variation of context in which the sequence occurs; means for comparing the first value to a first threshold and the second value to a second threshold; means for identifying that the sequence is a semantic unit based at least in part on the first value satisfying the first threshold and second value satisfying the second threshold; and means for outputting an indication that the sequence is a semantic unit based on identifying that the sequence is a semantic unit.