Grammar Focus: Relative Clauses (Non-Defining)

A non-defining relative clause gives extra, non-essential information. The sentence still makes sense without it.

Key rules:

• Always separated by commas.
• Cannot use 'that' — use who, which, whose, where, when.
• The relative pronoun cannot be omitted.

Examples: George Lucas, who created the universe, was influenced by Joseph Campbell. "Star Wars", which began in 1977, is a modern hero myth. Joseph Campbell, whose book is seminal, identified a universal pattern.