According to W. Mathesius, functional (actual) division of the sentence should be opposed to its formal division. Formal division presupposes the division of a sentence into its grammatical elements, while functional division deals with the ways of including a sentence into the overall context. Correspondingly, the main elements of formal sentence division are grammatical subject and grammatical predicate, and the main elements of formal sentence division are: a) the starting point (or basis) of the utterance, i.e. something that is known in the given situation (or may be easily understood) and from which the speaker proceeds; b) the nucleus of the utterance, i.e. something that the speaker informs about the starting point of the Utterance.
As a rule, each utterance of oral and written speech reflects the movement of the thought from something, that is already known, that is named by the speaker or is placed in front of the eyes of (he interlocutors to something that is still unknown to the readers or listeners. While forming the utterance the speaker takes into consideration the background knowledge of the addressee about the subject of speech and depending on this he makes the known part of the utterance the starting point of it, and in the second part he presents what he has to inform about the first part.
That is why, such division of the utterance into two parts – the theme (given, unknown) and rheme(new, unknown) – is called actual division (Functional sentence perspective). This division reflects the actual position of the speaker in a given (specific) case as regards the contents of the utterance and those the utterance is meant for.
The division into theme and rheme depends on the real context and specific speech situation: He’s got the book from a colleague He’s got a book from the colleague. Both sentences contain the same material information, but different actual information. The aim of the speaker in the two sentences is different: the first focuses on the book, rather than any other object, the second – on the person who gave him something.
