密歇根新闻广播 到底怎样算健康饮食?（在线收听）

Is it "healthy eating" or "healthful eating?" Is there even a difference?

For some people, there is. Anne Curzan, professor of English literature at the University of Michigan, is ready to lead us into the nuanced world of grammarians, where some distinctions are a little more complicated than they seem.

While Curzan was giving a talk on grammar pet peeves, someone expressed a moment of frustration: "People keep saying 'eat healthy food!' And I can't stand it!"

Although this might make you scratch your head, there is a rule behind it. In the 19th century, many grammarians sought to make words complement each other. They tried this with healthy and healthful. "To say healthful," says Curzan, "should mean 'conducive to or causing health,' and healthy should mean 'experiencing good health.'"

"The problem is that healthy has meant both those things for hundreds of years, and the distinction has never really held," says Curzan. "So I have to say I think this rule has not made it."

But this isn't the only place where grammarians tried to create complementary distribution in the language. There's another example: shall and will.

"In the first person," says Curzan. "In other words, with 'I' or 'we,' you use shall to express the simple future. Then you use will to express obligation, necessity, determination, or permission."

But if you use either word in the second or third person, the rules flip-flop. That means if you use you, he, or she, then will expresses the simple future and shall expresses permission/obligation/determination.

What were they thinking!? If you're looking for a grammarian to blame for this headache, Curzan suggests looking back at John Wallis, a 17th century bishop and mathematician. But don't be too hard on his memory, as the rule hasn't aged very well. According to Curzan, it's commonly used in just one place: legal writing, where the word shall expresses a legal obligation.

But this, too, is controversial, as the word shall is often misused. Lawyer Bryan Garner, an expert on legal grammar, has more or less given up on it. "His practice, at this point, is to always replace it with will or may or must in order to clarify," says Curzan.

It might seem like grammarians just make the rules, but sometimes they will be the first to break them.