"Focus" in linguistics, refers to subchannel encodings which accompany a primary signal. In writing we do things like "emphasis", EMPHASIS, _emphasis_, and in speech we extend the lengths, tone, and vibrato of pronounced words, or we mangle their pronunciation entirely by mutating the gross phonemic structure of entire words and phrases.
This is all VERY interesting to note, in the encoding of language in machines. Because resulting from the above, the connotations of "focus" must result in a signal receiver performing different semantic interpretations of the parent channel information, based on subchannel information. All said and done, this is not at all mysterious ... but it is a quantum of detail to be noted in the architecture of communications.
This is all groundwork for my study, in designing a new programming language environment for myself.