Words, phrases and clauses filling sentence element positions

When we looked at sentence/clause elements, we saw that these could be placed in certain positions or slots to create a sentence.  Sometimes these slots will be filled by one word, often by phrases.

        S (subject slot)         V (verb slot)       O (object slot)           A (adverbial slot)

              Merlin                    followed                 Arthur                        carefully.

The wrinkled, old wizard  was following    the crown prince          into the forest.

In the first sentence, each sentence element slot is filled by one word; in the second sentence, each slot is filled by a phrase.  We can define a phrase as a group of words, working together to fill a sentence element slot.

The above two sentences are simple, or single clause, constructions.  A single clause contains a minimum of a subject and verb, but can be quite a long structure with object and adverbial positions also filled.  It will only have one verb slot filled.

SV                Merlin shouted

SVO             Arthur raised Excalibur.

ASVOA          At that moment, Arthur raised Excalibur above his head.

AASVOA       That evening, cautiously, Merlin followed Arthur into the forest.

However sometimes a sentence element slot is filled by another clause, which contains its own verb:

SVO             Arthur, who was heir to the throne, welcomed the visitors.

The subject position in this sentence is filled by another clause, containing its own verb. 

Sentences usually contain a mix of words, phrases and clauses filling the sentence element slots. These terms occur in many of the different areas of grammar and we will revisit them often in relevant posts.