What are we to make of the verb will in this fairly simple-seeming sentence: If you’re not going to say something, I will. Verbs build clauses and clauses express thoughts, but what thought does the clause I will succeed in communicating?
One good skill grammar can teach us is close observation, the ability to look for the relationship between elements set closely together. The three basic elements in sentence structure are words, phrases, and clauses. A clause combines a subject with a verb, and that combination builds a thought. A sentence may have any number of clauses, but clear thinking obligates us to ensure that each clause is related logically to the one that precedes it. A sentence, in other words, should branch out from itself like a tree.
So when we analyze a sentence—which means when we try to understand what someone else is saying—we are best served to begin by looking for clauses, the representation of the thoughts someone wants us to consider. Our example has the two clauses you are not going to say and I will, and we should note, too, that the fact that the sentence begins with the word if marks it as a conditional statement: one thought will be the consequence of another. Since our procedure dictates that we begin at the beginning, let’s look closely at that elaborate first clause. In it we’ll find an answer to our original question.
English (like French) has a habit of using the verb go with an infinitive to indicate an immediate future, and that’s just what we see in the first clause of our sentence. The contraction you’re resolves, of course, into the subject you and the verb are, and that verb works with the participle going to form the progressive aspect. When the resulting are not going is followed by the infinitive to say, we have the essential gearwork to move the clause, the noun something coming along as direct object for the infinitive. We should see in all that grammar, though, one relevant point: the present tense in this first clause is pointing to the future.
When, then, we come to the second clause, with I as the subject and will the verb, we must first decide whether will is acting as a transitive verb in its own right. Does the clause mean to say that the subject wills something, as for example, I will all my possessions to my brother? Hardly. So the verb will must here be standing as an auxiliary verb, merely part of a verb phrase whose remainder remains unstated. And that, it turns out, is exactly what is going on. This second clause is a highly truncated version of I will say something, where the auxiliary verb builds the future tense, as it does regularly in English. And when an auxiliary verb works like this to point to the predicate preceding it, assuming for it all the meaning the grammar of the first clause can structure, such a verb is called a pro-verb, a term coined on the analogy of a pronoun, but written with the obligatory hyphen in order to distinguish it from the noun proverb.
The prefix pro– in both the words pro-verb and pronoun derives from Latin and means on behalf of. That can be instructive for both writer and reader to remember, because when something works to the benefit of something else, it’s best to be clear about just who that other party, called the antecedent, is. For a writer, confusion enters when the antecedent keeps too far a distance from its pronoun; and it behooves the reader, always, to look for the connection—sometimes grammatical, sometimes logical—between clauses one after the next. We might go so far as to say, in fact, that the closer the connection, the more meaning there is. And that’s really what we’re reading for, right?