A subject - verb - adverbial sentence consists of a subject See the glossary definition , a copular verb See the glossary definition , and an obligatory adverbial See the glossary definition . The subject is always filled by a noun phrase or a nominal clause. The adverbial is obligatory. The sentence will not be complete, or grammatical, without it. A subject - copula - adverbial sentence could be as simple as the example below:
The subject is a one-word noun phrase. The verb is the commonest copular verb (be) and the adverbial is a prepositional phrase. The adverbial is obligatory; without it the sentence would not make sense except perhaps are a short answer to a question (Which animals are in danger? Koalas are.).
However, noun phrases and adverbials can be long and complex so most SVA structures are much longer, as in some of the examples below (click and drag to stop, start and find the sentence you wish to examine):
You can view an analysis of some of the noun phrases in the above examples in the animations below (click on Subject to view each noun phrase).
In the above example the head of the subject phrase is "carbon dioxide". It is a compound noun and has no modifiers. The adverbial is a double one "there" is an adverbial of place and "for hundreds of years" is a prepositional phrase (one embedded See the glossary definition in another).
In the above example the head of the subject phrase is "species" and there is one postmodifier, Rhizanthella gardneri. This is an appositive noun phrase. It is the name of the species (a type of orchid). The adverbial (in Western Australia) is a prepositional phrase, specifying location.
In the above example the head of the subject phrase is "phase" premodified the adjective phrase "most intense" and postmodified by the prepositional phrase "of each event". The adverbial is a noun phrase "half a year". Noun phrases are rare as adverbials but they do occur, mainly as time or date adverbials.
In the above example the head of the subject phrase is "answer" postmodified by the prepositional phrase "to this question". The adverbial is also a prepositional phrase "in how our brains are hardwired to think". This has the preposition "in" and its complement is a nominal See the glossary definition in the form of a wh-clause See the glossary definition "how our brains are hardwired to think".
Most sentences contain one or more optional elements as well as those strictly necessary to form a grammatical construction. Here is a simple example: The first adverbial "In the UK" is not part of the SVA constriction. It is an optional element and the rest of the sentence is an acceptable grammatical structure without it. All the other elements are obligatory.