19. English - Mastering Commas in Defining and Non-Defining Relative Clauses

Mastering commas in relative clauses is essential for clear writing. The core error involves misusing commas with defining and non-defining clauses. Defining clauses provide essential information to identify the noun; therefore, they never take commas. For example, "The car that I bought is red" needs no punctuation. Conversely, non-defining clauses offer extra, non-essential details and must be enclosed in commas, as in "My car, which is red, is fast." Writers frequently make the mistake of isolating essential defining clauses with commas or omitting them around non-defining clauses, completely altering the sentence's meaning and logical flow.