Supplementary support for language you've already met in the course. Nothing here is a required stage — use it whenever a point needs more work.
Quick checks drawn from the Grammar Bank. Try it, then reveal.
Defining = essential, no commas, 'that' allowed. Non-defining = extra information, commas, never 'that'.
Join: 'This is the flat. We rented it last year.'
Add extra info: 'Our CEO started here as an intern.' (non-defining)
Drop the relative pronoun + be: '-ing' for active meaning, past participle for passive meaning.
Reduce: 'The man who is standing by the door…'
Reduce: 'The files that were deleted yesterday…'
