Writing complex sentences

Complex sentences

A complex sentence is formed by adding one or more subordinate (dependent) clauses to the main (independent) clause using conjunctions and/or relative pronouns. A clause is a simple sentence. Simple sentences contain only one clause (verb group). Complex sentences contain more than one clause (verb group).

In technical, scientific and mathematical writing the logical relationship between the items that the conjunctions connect is not made explicit and introduces comprehension complications. These writing genres bring the challenging elements of unfamiliar vocabulary including jargon and technical words, lexically dense sentences and an element of ‘guessing’ or interpreting the data in relation to the task. For many students the concepts or subject matter are unfamiliar and therefore problematic.

For example:


  1. The ice melts as the temperature rises. Students have to interpret causality in the sentence “The ice melts as the temperature rises” as meaning that the events happen simultaneously and the rise in temperature causes the ice to melt.
  2. The sugar dissolves when placed in water. This means that the sugar dissolves when it is placed in water because water is a solvent. Here the ellipsis of it is’ increases the difficulty for students.

None of these meanings are made explicit but have to be ‘recovered’. Causality has to be inferred from the sentences using the student’s knowledge of grammar and the water acting as a solvent has to be inferred from students’ contextual knowledge of the subject.

Constructing complex sentences

Complex sentences result when other more sophisticated devices are used to join clauses; this means a subordinate (dependent) clause is joined with a main (or independent) clause.

There are three main ways to join clauses to make complex sentences. By using:

  • relative pronouns – that, which, who, whose.
  • conjunctions (subordinating) – while, because, although, as, when, until, unless, through, by, since, whenever, if, where, before, etc.
  • verb structures (non-finite) – (participle) verb forms that end in –ing or –ed or an infinitive verb form such as to go, to become, to see.

This PowerPoint, developed by teachers, may be useful in helping your student understand how complex sentences are constructed.

Activities to support the strategy

Activity 1: modelling clauses through shared and modelled reading

Use current classroom texts and or select suitable texts online

  • Students have a wide range of clause combinations read to them through quality texts with the clause grouping emphasised through intonation and pausing.
  • Students identify simple, compound and complex sentences (including main and subordinate clause/s) as they read or as sentences are read to students.
  • Students identify the number of ideas contained within modelled sentences from texts and then identify which idea is the main (independent clause) that can stand on its own.

Activity 2: innovating on authentic texts and using students’ own work

  • Change two sentences into a compound sentence.
  • Change several sentences into one complex sentence.
  • Add adjectival clauses to describe the nouns and make the sentence more interesting.
  • Add adverbial clauses to modify the verbs and make the sentence more interesting.

Activity 3: worksheets for embedded clauses

Use the following website to access the worksheets to initially teach from and then to practice in small groups.

Activity 4: sentence work games

Using the resources cut up and laminated, firstly explicitly teach using them and then using one or more dice have groups of students either orally or as a written activity follow the game rules.


Australian curriculum

ACELA1507: Expressing and developing ideas: Understand the difference between main and subordinate clauses and that a complex sentence involves at least one subordinate clause.

NSW syllabus

EN3-6B: Outcome 6: uses knowledge of sentence structure, grammar, punctuation and vocabulary to respond to and compose clear and cohesive texts in different media and technologies (EN3-6B) - Understand and apply knowledge of language forms and features: understand the difference between main and subordinate clauses and that a complex sentence involves at least one subordinate clause.

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