When we talk about grammar, we’re really talking about the structure beneath our language,
and understanding that structure is the key to getting little mechanical details like
commas right.
The first step is identifying the two pillars upon which the whole structure rests.
The subject and the predicate are less things than they are roles, and we define them by
their relationship to each other, kind of like we define a “brother” or “sister”
by relationship.
It makes them incredibly versatile – especially the subject.
That’s great for our speaking and writing and thinking, but it can make the subject
hard to pin down with any single definition.
We’re going to try it, but first, let me offer a simpler definition: the subject is
usually (1) the noun that serves as the topic of the sentence, (2) at the beginning of the
sentence, and (3) the doer of the action in the sentence.
Let’s look at a simple example: “The robot dances.”
What’s the noun that serves as the topic, the beginning of the sentence, and the doer
of the action?
The robot.
That’s the subject.
And it remains the subject even if we add a lot of other information: “The robot dances
through a crosswalk in front of a Walgreens.”
The robot is still the topic, the beginning, and the doer.
In more complicated sentences, we sometimes have to settle for two of three.
An introductory phrase can push the subject away from the beginning: “After being painted
in rainbow stripes, the robot keeps dancing.”
Because the robot is still the topic and the doer, we know it’s still the subject.
A sentence can also be flipped into passive voice, which takes the doer out of the subject
slot: “The robot is being upstaged by two visored humans.”
The humans are doing the upstaging, but the robot is still the topic and the beginning,
so we know it’s the subject.
But sometimes something other than a noun gets shoved into the subject slot, like a
verb phrase: “To dance with a robot is divine.”
The subject is “to dance.”
Other times a whole clause can serve as a subject: “All the boy wants is to dance
the robot in front of Buckingham Palace.”
The subject is “all the boy wants.”
And that clause has its own subject, “the boy.”
As you can see, it can get pretty complicated, and that’s why these simple definitions
ultimately come up short.
It’s also why the best way to recognize a subject is to consider its relationship
with the predicate.
Trying to do otherwise is like trying to define “brother” or “sister” without mentioning
a sibling.
Because the link between them is the foundation of our sentences, a more functional definition
for a subject might be: the element that controls the predicating verb.
Whether the subject is a noun or not, that verb should always remain in lockstep with
it, like a dancer following its partner’s lead.
When we say, “The robot dances,” for example, we choose the form of that predicating verb,
“dances,” based on the subject.
The robot dances, but the robots dance.
The subject controls the form of that verb.
And that’s true of all the examples we’ve looked at.
The robot is upstaged by humans, but the robots are upstaging the humans.
To dance is divine, but two dancing robots are divine.
Now, in English, unlike some other languages, we have a lot of conjugations that remain
the same across different perspectives: I danced, you danced, she danced, they danced.
Even so, the subject – I, you, she, they – has control of the verb in a way that
you can probably sense with your natural intuition as an everyday language user.
That control will remain no matter what form the subject takes, where it occurs, or how
many there are in a sentence.