English - Advanced Grammar - Relative clauses - Defining vs Non-defining
5 steps: (1) RELATIVE CLAUSES add information about a noun using who/which/that/whose/where/when. 'The man WHO lives next door is a doctor.' (2) DEFINING (essential): tells us WHICH one. No commas. 'The students WHO passed the test can leave.' (which students? the ones who passed). Remove it and mea