Here is my total knowledge of the subjunctive, such as it is:
Verbs are moody. They have three moods. One mood is the indicative, which is a statement or a question. One mood is the imperative, which is a command or an order. And one mood is the subjunctive, which is...ah...not used much any more, thank goodness.
You use the subjunctive when you want to set up a situation that doesn't actually exist but could if things were different. I'm aware of it most often with the verb "to be." Normally, the first-person past tense of the verb "to be" is I was. But with the subjunctive, the first-person past tense of the verb "to be" is I were. Thus, you would say "If I were taller, I would look thinner" and not "If I was taller, I would look thinner."
If I have this all wrong, feel free to comment.
Now, I almost got through life without knowing the first thing about the subjunctive. (And even now I probably know only the first thing about it.) However, when I was in college my boyfriend invited me to his home to meet his family. Before the big day, said boyfriend became all apologetic and said something like, "I've got to warn you about my father."
I'm thinking, What? Does the guy walk around in his boxers? Chew tobacco and spit? What?
No. "My father knows you're an English major, and he's sure to ask you about the subjunctive. He's got a thing about the subjunctive."
Now, keep in mind that my boyfriend didn't actually know what the subjunctive was, himself. In fact, he was an engineering student and his father was an engineering professor. Why did any of them ever talk about the subjunctive at all?
So I had to hit the books in order to meet my boyfriend's father.
Even so, I did not have a good grip on the subject. And, sure enough, it did come up. I don't recall how, but my boyfriend's father did start talking about it, and he ended the subjunctive conversation with, "It is my favorite mood."
These kinds of things used to happen to me quite often. People would say things to me like, "Hey, you were an English major, right? So what's the difference between a clause and a phrase?"
You know how anyone with any kind of medical training at all will have people ask her to look at their moles? Well, I used to get the same thing, only about grammar and usage.
I probably would do better looking at moles.
Not everyone suffers from grammar and usage anxiety the way I do. We will cover that in Grammar and Usage, Part III.