Definitions Theme

Markedness and themes

There is a good deal more on the meaning of markedness later in this guide. For now we'll just consider it in relation to the communicative purpose of an utterance or written text.
It is true that in most simple declarative utterances the theme and the subject are often the same thing but that is not always the case and things can become more complex, as we shall see. So, for example, in:
My mother did the work on Tuesday
we have the theme (my mother) which also happens to be the subject of the verb, do. That sentence is unmarked.
However, in:
The work was done on Tuesday by my mother
the theme is the work which is grammatically still the subject but functionally the patient in a passive clause. In this case, the sentence is marked because the speaker / writer has deliberately chosen to place the work in theme position.
And in
On Tuesday, my mother did the work
the theme is on Tuesday because it is raised to mark it for emphasis.
The important point here is that when the theme and the subject are the same, the word order, in English, is described as unmarked, i.e., it carries no special communicative force.
This is only true for declarative sentences. In interrogative sentences, the theme is the finite verb:
May we come in?
and in imperative constructions, it is usually the Predicate because the subject is generally absent:
(You) stop that!
When the subject is present, that becomes the theme:
You try!
It is also the case that the theme can be made up the whole of an adverbial, a noun phrase or a prepositional phrase including any modification.
All of these examples are of what is called, for obvious reasons, a topical theme and that may be defined as
the starting point from which experiences are unfolded in a clause
(Butt et al, 2001: 136)
Topical themes such as the ones identified here are also all simple themes because they consist of one element only, although that element may be quite complex grammatically as the examples reveal.
When a topical theme is the only theme in a clause, it is normally just called a theme. There are, however, two other types of theme that this guide will consider (eventually).

Rheme

The rheme may be defined as:
everything else that follows in the sentence which consists of what the speaker states about, or in regard to, the starting point of the utterance
(Brown and Yule, 1983: 126/127)
So, in all the examples above, the rheme is what follows the theme (all of it).
The term rheme is another communicative category, not a grammatical one. The grammatical term with which it is sometimes confused is predicate which is defined as the part of the sentence which says something about the subject. So, for example the underlined parts of these sentences are the predicates:
Yesterday, Paul went for a walk
Surprisingly, she refused the job
because they tell us about the subject of the sentence. However, seen communicatively, the rhemes of these sentences are:
Paul went for a walk
and
she refused the job
because raising the adverbial to the front of the sentence has marked it as the theme and all that follows, including the subject of the verb is the rheme.
In this case, we actually have a different sort of theme in the second sentence, called an interpersonal rather than topical theme (realised with the word surprisingly) because it expresses how the speaker feels. More on that later.