Relative and adverbial clauses are the important extra parts of a sentence that add more information. They are used in every type of writing and should be included in an IELTS essay.
Definitions – not so important
Relative clauses add details to the subject.
Adverbial clauses add details to the verb in a main clause.
Adverbial clauses can be introduced in many different ways.
Relative clauses usually involve ‘that’, ‘which’, ‘who’, ‘why’, or ‘where’.
The definitions are not particularly important (most English speakers don’t know what the terms are). Knowing how to use them, however, is very important in order to achieve better writing.
A guide to relative clauses can be read here and here.
A guide to adverbial clauses can be read here.
Adding background and detail
The idea of adding these clauses is to include more background and detail. The history and consequences of the main clause and subject are a good place to start.
Another tip is to think of the question words (what? how? who? where? etc.) and answer them as best as possible within the sentence.
Example of building up a sentence through detail
The First World War claimed the lives of over 9 million people.
The First World War claimed the lives of over 9 million people across the globe. (where)
The First World War, which was started when the assassination of Franz Ferdinand lit the powder-keg of European alliances, claimed the lives of over 9 million people across the globe. (background history)
The First World War, which was started when the assassination of Franz Ferdinand (the heir to the Austria-Hungary empire) lit the powder-keg of European alliances, claimed the lives of over 9 million people across the globe. (who)
Lasting from 1914 until peace was officially signed in 1919, the First World War – which was started when the assassination of Franz Ferdinand (the heir to the Austria-Hungary empire) lit the powder-keg of European alliances – claimed the lives of over 9 million people across the globe. (when)
Lasting from 1914 until peace was officially signed in 1919, the First World War – which was started when the assassination of Franz Ferdinand (the heir to the Austria-Hungary empire) lit the powder-keg of European alliances – claimed the lives of over 9 million people across the globe in a series of heroic yet tragic battles. (how)
(Note: most sentences aren’t as long as this, but it is an example of how a longer sentence can be built)
The importance of punctuation
Three punctuation marks offer great help when adding information:
, (comma)
( ) parentheses
– – dashes
Consider how unreadable the above example is if using only one type of punctuation:
Lasting from 1914 until peace was officially signed in 1919, the First World War, which was started when the assassination of Franz Ferdinand, the heir to the Austria-Hungary empire, lit the powder-keg of European alliances, claimed the lives of over 9 million people across the globe in a series of heroic yet tragic battles.
Vary punctuation to keep the sentence structure clear.