There are many hundreds of character-representing SDATA entities defined in Annex D.4 of ISO 8879, the SGML standard, and many more are in use. There is usually a convention for constructing their names. The use of patterns to match their names allows whole classes of entities to be processed by a single translate rule.
Patterns already provide mechanisms for alternation (| or or) and for capturing matched text. This allows more than one name to be matched, as in the accented letter example. With the very large number of different characters in use, and the general use of SDATA entities to represent them, some way of managing large sets of names is required. This is provided by the translate rule.