1. An apparatus for identifying one or more words corresponding to a sequence of sub-word units output by a recognition system in response to a rendition of the one or more words, the apparatus comprising: first receiving means for receiving the recognised sequence of sub-word units representative of the one or more words to be identified; second receiving means for receiving a plurality of dictionary sub-word sequences, each representative of one or more known words; means for comparing sub-word units of the recognised sequence with sub-word units of each dictionary sequence to provide a set of comparison results; means for combining the comparison results obtained by comparing the sub-word units of the recognised sequence with the sub-word units of the same dictionary word to provide, for each dictionary word, a measure of the similarity between the recognised sequence and the dictionary sequence; and means for identifying said one or more words using the similarity measures provided by the combining means for all the dictionary sequences.