Garner’s Usage Tip of the Day: that (1).

that (1). Today: And “which.” You’ll encounter two schools of thought on this point. First are those who don’t care about any distinction between these words, who think that “which” is more formal than “that,” and who point to many historical examples of copious “whiches.” They say that modern usage is a muddle. Second are those who insist that both words have useful functions that ought to be separated, and who observe the distinction rigorously in their own writing. They view departures from this distinction as “mistakes.” Before reading any further, you ought to know something more about these two groups: those in the first probably don’t write very well; those in the second just might. So assuming you want to learn the stylistic distinction, what’s the rule? The simplest statement of it is this: if you see a “which” without a comma (or preposition) before it, nine times out of ten it needs to be a “that.” The one other time, it needs a comma. Your choice, then, is between comma-“which” and “that.” Use “that” whenever you can. A restrictive clause is essential to the grammatical and logical completeness of a sentence. A nonrestrictive clause, by contrast, is so loosely connected with the essential meaning of the sentence that it could be omitted without changing the meaning. Hence, three guidelines. First, if you cannot omit the clause without changing the basic meaning, the clause is restrictive; use “that” without a comma. Second, if you can omit the clause without changing the basic meaning, the clause is nonrestrictive; use a comma plus “which.” Third, if you ever find yourself using a “which” that doesn’t follow a comma (or a preposition), it probably needs to be a “that.” Next: Relative Problems. For information about the Language-Change Index click here. ——————– Quotation of the Day: “Good usage is more necessary in written than in oral discourse. In oral discourse, tone of voice and body language help bridge the chasm of meaninglessness between the speaker and the audience. In writing these helps are absent and the bridge over the chasm must be all the more carefully paved.” John W. Velz, professor of English from 1954 to 1996.