Usage and Grammar

Q. We have a disagreement in my office as to the usage of “this” as a pronoun. “The cooling holes were originally defined using two points. This was later revised to a start point and compound angles.” My coworker thinks that I need to add “definition” after “this.” While I agree it is a good idea in many cases to eliminate ambiguity, I don’t think it is required in this case. Is he right?

A. Your coworker makes a valid point in that “this” has no antecedent and is left dangling. Most readers will mentally supply “definition” or “idea,” but the reader does have to supply something. If you changed “this” to “these,” the referent could be taken to be “points,” and you would be on firmer ground, but even then, there might be initial confusion over whether “these ” referred to “holes” or “points.” Although most readers would probably follow your reasoning, for the sake of precision and clarity and grammar, I’m with your colleague.