Let’s consider the grammar (not the politics) of this sentence: A filibuster is when a senator tries to delay a vote by making a long speech. At first blush, it seems to be an acceptable statement, certainly a sentence construction we hear often enough in relaxed and easy conversation. From the standards of the written word, however, this unassuming sentence is disjointed, and we can revise it easily by understanding what is called an adverbial clause.
We know that a clause is a group of words with a subject and a verb, and we know too that clauses are classified as either independent or subordinate. Pennsylvania Avenue connects the Capitol with the White House is an independent clause because in reading it, we have all the information we need to comprehend an idea. On the other hand, when I go to Washington, for example, is a subordinate clause because reading it leaves us wanting; it sets us up to expect more information essential to bring the thought to completion, but it does not supply that information itself. Subordinate clauses begin with subordinating conjunctions (some of the more common are when, since, if, because, that), and they exhibit one peculiarity of importance to us here: subordinate clauses in their entirety can function as a noun, adjective, or adverb.
As odd as that may sound, all it means to say is that the clause when a senator tries to delay a vote by making a long speech is an adverb—all thirteen words together, not just the word when or any other word or phrase alone in the clause, but the entire subordinate clause as an entity in itself. Adverbs, we know, answer the question when?, and so we are immediately alerted to the adverbial function of the clause when we read that opening subordinating conjunction. We can name this subordinate clause, then, an adverbial clause, the better to help ourselves see for purposes of analysis the three sections of the frame or skeleton of the sentence: the subject a filibuster, the verb is, and the adverbial clause when a senator tries to delay a vote by making a long speech.
And this quick analysis will reveal where the problem lies in the construction of the sentence. The verb is intends here to define the subject a filibuster, to tell the reader what a filibuster is, to say what it is, not to give an instance of it. In this function of defining, the verb is acts as a copula, a verb that links or identifies a subject with a noun, pronoun, or adjective in the predicate. But our analysis has shown us that the predicate of this sentence contains an adverb (in the form of an adverbial clause), not a noun, pronoun, or adjective. And therein lies the cause of the imbalance. Change the adverbial clause to a noun, for example the noun tactic, and our revision will be complete: A filibuster is a tactic that senators use to delay a vote, or as the official United States Senate website (senate.gov) puts it: A filibuster is the use of time-consuming parliamentary tactics by one Senator or a minority of Senators to delay, modify, or defeat proposed legislation. Perhaps the noun use is appropriately less pejorative than tactic.
Subordinate clauses, then, can act as adverbs, but they can also act as nouns and adjectives. In the sentence I deny that this bill will help the ordinary working family, what I am denying—and remember that the word what is asking for a noun—is that this bill will help the ordinary working family, a subordinate clause now answering as a noun (and appropriately called a noun clause). And in the sentence Voters will remember the senators who voted for this bill, the subordinate clause who voted for this bill is defining the noun senators, and is therefore an adjective in the form of an adjective clause.
Once again we can see how some straightforward analysis can help us find exactly where our sentences may be going wrong. Terminology, here and in every other study, tells us what to look for, sometimes finding it to confirm what we’ve written, other times to correct it. Either way, a fuller understanding of sentence structure and its nomenclature can give us confidence, without which very little can ever get done.