Not too long ago, I came upon this sign taped to the door of a medical office: Covid-19 Test: Going Through This Door. It’s fair to say, I think, that we all know what the notice meant: that one should use that door to get to the Covid testing site. From a grammatical point of view, though, the mishap offers an opportunity to review some basics about English grammar, and to remind us as well that much can depend on a few simple letters.

First, the sign was meant as a direct command. The writer of the notice intended to determine the action of certain readers, those looking for a Covid-19 test, but in doing so he or she chose the word going instead of go to express that command. Ordering other people about is, indeed, one of the things we can do with language. We can also state a fact or express an emotional reality, and all three of these uses of language—fact, command, and wish—make up what is called the mood of a verb.

English verbs have three moods that correspond to these three uses: indicative, imperative, and subjunctive. We form the indicative by including the subject along with the verb: This door leads to the Covid-19 testing site. Such a construction is stating a fact; it intends to convey information, not direct the action of someone else. The imperative mood, by contrast, is intent on telling others what to do, and to indicate that intention, we drop the subject pronoun and use the verb alone: Go though this door. The subjunctive mood, finally, is interested not in public facts but private mental realities, and although it would be rare to see it on a sign, we could say, I hope you might go through this door to get your Covid-19 test. Strange but true.

But if the sign at the medical office should have said go instead of going to express the imperative mood, what is the grammar of going? Words that end in –ing are either participles or gerunds. A participle is an adjective built from a verb. Something that goes is a going something, just as someone who talks is talking, a talking person. Because they are formed from verbs, participles point to the active characteristics that something exhibits. I might be wearing a white shirt, and the adjective white names the quality of whiteness that describes the shirt. But if I had the temerity to go out in public in a torn shirt, the quality of being torn—the fact that the shirt can be described as torn—is only apparent because something happened to it. Participles name qualities that are present in things only by virtue of an action taken upon them.

The other kind of word that ends in –ing, the gerund, is not an adjective but a noun built from a verb. The world, as it happens, is an odd place, and when we come to think about it, some things exist only when they’re moving. I might tell you that I love running, but the second my legs stop moving at a certain speed in a certain way, running has disappeared into nothingness—unlike the pencil on my table in this room. Gerunds give us a way to express the difference between static and dynamic realities, both of which go into making the world what it is to us as seen through language.

So when that sign on the door read Covid-19 Test: Going Through This Door, it either meant that the test was going through this door (in which case going would be a participle), or that the act of going through this door would take you to the test (in which case going would be a gerund). But we’d have to work hard to make either of those explanations plausible, because the first doesn’t make any logical sense and the second is only a fragment of the idea. Better to conclude that I stumbled upon what is called a solecism, a grammatical mistake, and realize how difficult and subtle language can be.

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What is the difference between a preposition and a conjunction? The question can help us see that writing a good sentence—and understanding what we’ve written—involves not just finding the right words, but combining those words into meaningful groups. Being able to see word groups dissolves many a grammatical problem, and can even suggest new revisions to a sentence that may not be saying what we want to say in just the right way.

Both prepositions and conjunctions fall under a broad grammatical category called connectives, but each has a defined role to play in building out a sentence. Whether a word is a preposition or conjunction will often depend on the other words with which it is working. Grammar is contextual, which means the same word can function as a preposition in one sentence and as a conjunction in another. Prepositions show the relationship, or connection, between one thing and another, whether that relationship is literal (a pencil on the table) or figurative (a lecture on gardening). Conjunctions, like the word and, for example, also show a connection, but the relationship can’t be physical: to say pencil and paper is to associate two things, a pencil and some paper, in our mind, not in relation to something else in the physical or figuratively physical world.

We can see the difference between these two parts of speech more easily if we keep in mind the rules that oversee their composition. A preposition must have an object, most often a direct noun: in the group of words on the table, on is the preposition and table is its object, the two beginning and ending what is called a prepositional phrase. When grammar talks about an object, it means something other than something else. So in the prepositional phrase a pencil on the table, the preposition on intends to relate two isolated things in regard to their position to each other. But if I want to expand the idea and say that a pencil and paper were on the table, the conjunction and is indeed joining two things, pencil and paper, but it is joining them together as one conception: I am saying, in effect, “Think of these two things as one, and now relate that pair to something else in regard to position, namely, the table.” That, believe it or not, is all going on in our minds (thankfully unconsciously) in a sentence even as simple as pencil and paper are on the table.

But the plot thickens. As it happens, the same word can often function as either a preposition or a conjunction, given the other words it works with. Consider the word than, for example, in these two sentences: he has more than $10,000 in the bank and he has more in savings than I have. In the first sentence, than is a preposition, with $10,000 standing as its object (the word more is an adverb modifying the verb has), and it is connecting the money to the bank, two very different things. In the second sentence, though, the word than is a conjunction, which we can first see by the fact that it has no object: the words I have form a clause and represent an action, not a thing. And that is in keeping with what we have already observed about conjunctions: they connect ideas, not things. Here the conjunction than means to connect his savings and my savings, how much he has and how much I have. The sentence with the conjunction wants to talk about the idea of having savings, not the money itself, though that subtle difference will be dramatically realized were I to request a certain withdrawal.

The practical observation to make for revision, then, is that prepositions always have an object in the form of a noun. Preposition and object together form a prepositional phrase, and that phrase can often transform itself into a clause, helping us elaborate the idea for emphasis: he has more than $10,000 in the bank, and that’s a lot more than I have. It’s true that we generally try to reduce the number of words we’ve written revision to revision, but sometimes we need to extend an idea to carry its meaning through. Looking at the grammatical structure of what we’ve written can suggest possibilities that might otherwise go unnoticed, with the aim of making these changes more automatically (or unconsciously) after we’ve once become conscious of the structure of the language.

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In studying grammar, it can be helpful—or inspiring or consoling even—to remember the difference between complex and complicated. When we say something is complex, we mean that it has many different parts, all working smoothly together as an intricate system. When we say that something is complicated, though, we mean that it has many different parts, but we can’t see how they all work together and we’re not really sure they even do. Something that is complex can be beautiful; something complicated, never.

All of the pieces of grammar, what are called the parts of speech, are more complex than they are complicated, for they do largely work together successfully as a system. But that cooperative complexity can be a challenge at times to see. How, for example, are we to understand the two instances of the word what in this simple exchange between two friends: What more do you want? I told you what he said. The parts of speech help us classify how a word can be used grammatically, and in both instances here, the word what is a pronoun, a word that is being substituted for another word, usually a noun or an element being used as a noun. But to say that what is a pronoun doesn’t answer much because there are, by some reckonings, eleven different ways a pronoun can be used. Complexity, indeed.

The first sentence is posing a question, and we know that because the verb do, auxiliary to the verb want, stands before the subject of the sentence; subjects usually precede their verbs, and so the inversion here signals that a question is being asked. As the first word of an interrogative statement, the word what confirms the question, and so we can be sure that this instance of the word what can be explained as an interrogative pronoun, one of those eleven uses of a pronoun. And we can appreciate the intricacy one step more by understanding that this interrogative pronoun is presenting itself as the direct object of the transitive verb want, which we can see if we unwind the word order back into its declarative form: you want what.

Now the second sentence wants us to sharpen our sword. The first observation to make in analyzing the sentence I told you what he said is that the statement is made up of two clauses, I told you and what he said. We can dispose of the first clause easily enough: I is the subject of the transitive verb told, and you is its indirect object. Transitive verbs, as we know, have direct objects, so if we ask what it is that was told, we would have to answer with the entire second clause: what he said. This second clause, then, is in its entirety the direct object of the transitive verb told. But how does it work in its own right and how is it connected to the first clause?

This second clause begins with the word what, but unlike the first sentence we examined, what is not here an interrogative pronoun but a relative pronoun, and what is called a compound, or double, relative, to boot. All relative pronouns connect clauses in a sentence by substituting in their own clause a word that refers to a noun in another clause, the identification bringing the two clauses into relationship; we do this all the time in sentences like the film that I saw last night was fantastic, where the relative pronoun that refers in its own clause (that I saw last night) to the noun film in the main clause (the film was fantastic). That identity of meaning but difference of grammatical use fuses the two clauses into one meaning.

A compound relative pronoun, though, brings an interesting twist to this configuration. The word what in the second clause really means that which, and when we unpack the word like this, we can see that it is made up of the demonstrative pronoun that (yet another of those eleven uses of a pronoun) together with the simple relative pronoun which in reference to it. So to say what he said is really to say that which he said; that is the object of the transitive verb told in the first clause, and which is the relative pronoun referring to that, which in turn is the object of the transitive verb said in the second clause. The double relative double weaves the syntax between the two clauses, producing a tight, sure, brief statement. All of which makes it strange but true to say that grammatical complexity can be at times a way to concision, one of the high achievements of good writing.

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One of the fundamentals of English grammar is that a verb agrees in number with its subject. When we think of a verb, we probably think first of tense, the time when the action is occurring. But verbs also have number, meaning singular and plural. If the subject is singular, the verb should be singular; if plural, plural. Both tense and number are two (of five) properties of a verb, and determining the number of the verb can be risky at times.

Here’s a short passage that is describing the character of someone: He loved the outdoors, all of it: bugs and rocks and dogs and water. But what he loved most were the trees. The first sentence gives us the context for the second, and it is the verb were in the second sentence that directly concerns us here. Were is a plural form of the verb to be in the past tense (was, by contrast, is a singular form), and the question before us is whether were should be was: But what he loved most was the trees.

When we are in doubt about the construction of a sentence, it is always good procedure to begin by separating the subject from its predicate; this will put the subject term into some relief so that we can examine it more easily. Thus: But what he loved most | were the trees. The number of the subject determines the number of the verb, and the subject here, what he loved most, is a bit involved. Read it again closely and you will see that what he loved most means that which he loved most. The word what in such a construction is called a double relative; it stands both for the demonstrative pronoun that and for the relative pronoun which. We recognize which he loved most as a restrictive relative clause whose antecedent is the pronoun that, and those two elements, pronoun and relative clause, together comprise the subject of the sentence.

Now we’re in a position to see that the pronoun that is singular (its plural form is those), and so we have the evidence we need to conclude that the verb for this subject phrase should be singular, not plural: But what he loved most was the trees. So what might be behind the writer’s mistake? The passage is filled with plural nouns: bugs and rocks and dogs, even the outdoors itself is a plural noun in singular construction (which is why, by the way, its pronoun, it, is singular), and so the writer’s cast of mind, so to speak, is in a plural world. But even more determinative is the fact that the noun in the predicate of the sentence, trees, is plural. The proximity of this plural noun to the verb will influence many a good writer, particularly so amidst so many other plural nouns in the context, with a complicated singular subject phrase to boot. But the subject is singular, no matter how involved, and so its verb should remain singular as well.

Such a lapse falls under a grammatical concept called, oddly, attraction; the number of the verb (were) has been attracted by the number of the noun in the predicate (trees), and the attraction proved fatal. Not all attraction, grammatical or otherwise, is so consequential, but when the subject and verb do not agree in number, the match can be misleading. The worry is not about grammatical etiquette but of accuracy, of clarity. If the body and bulk of what we read and write is clear and sure, then we are better able to appreciate the intentional lapses that a good writer will undertake in literature and poetry to help us see what we commonly see in an uncommon way. And then the attraction isn’t fatal but playful, as language full of life should be.

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