Many authors and most readers don’t understand the important distinctions between “which,” “who,” and “that.” Now you can be better writer, avoid confusing readers, and boast of being smarter than a fifth-grader.
Always use who when referring to people, never that or which.
Restrictive clauses are introduced by that or who, never which. You know a clause is restrictive when its removal causes the remaining parts of the sentence to be untrue. Never use commas to set off restrictive clauses.
Explanatory clauses are introduced by which or who, never that. You know a clause is explanatory when its removal does not cause the remaining parts of the sentence to be untrue. Always use commas to set off explanatory clauses.
Restrictive Examples, always with no comma, using that or who, never which:
- My friend who usually phones every day hasn’t called in three days. (Restricts the meaning to a particular friend.)
- The person who traveled the greatest distance should get the prize. (Restricts the meaning to one person.)
- Companies that don’t have a good business plan have a high risk of bankruptcy. (Identifies a smaller group within all companies.)
Explanatory Examples, always with commas, using which or who, never that:
- My best friend, who usually phones every day, hasn’t called in three days. (Explanatory, because we can have only one “best friend.”)
- Tim Andrews, who traveled the greatest distance, should get the prize. (Explanatory, since we have only one “Tim Andrews.”)
- The classrooms and hallways, which were painted during summer break, made the old school look new. (Explains what was done to all the classrooms and hallways.)
