The WWP uses the <emph> element to encode renditionally distinct words or phrases which convey linguistic or rhetorical emphasis, and which are not encoded with a more specific element (<quote>, <name>, etc.). Renditional distinctness in this case means renditional shifts which apply to the entire word (such as italics, small caps, all caps), not initial capitalization.
In our earlier texts, which highlight large numbers of words, it may be difficult to draw a clear line between emphasis and other reasons for renditional distinctness, and particularly between the use of <emph> and the WWP element <mcr>. In general, <emph> should be used only where it is fairly clear that some rhetorical or linguistic emphasis is intended, for instance to point a contrast (see examples); in texts which highlight every noun, one should tend to use <emph> only rarely. But in later texts, where highlighting is less frequent and less routine, one might be more likely to assume that highlighting serves to convey an actual rhetorical emphasis in the highlighted words.