今天的《词汇大师》讨论的是动名词和不定式，在许多主谓句中动名词和不定式都可以使用，我们只要记住不定式 to+verb 语义比较正式，对比一下：Swinming is a good exercise. To swim is a good exercise……

AA: I'm Avi Arditti with Rosanne Skirble, and this week on Wordmaster: more of our discussion of gerunds and infinitives with English teacher Lida Baker.

RS: A gerund, remember, is a verb ending in -ing but used as a noun. An infinitive is a verb with the preposition "to" as in to go, to swim, to walk.

AA: Huy Doan in Vietnam asks about the verb "regret." He wants to know if the verb that follows it should be a gerund or an infinitive, and what's the difference? We asked Lida.

LIDA BAKER: "If we have a sentence like 'I regret to inform you that you have not been accepted to the university of your choice,' that's a correct sentence. In contrast to that, if we say something like 'I regret buying that car,' that's also a correct sentence. So what's the difference? OK, with this verb, and with a few other verbs, the choice of infinitive or gerund has to do with which event happened first. If I say 'I regret buying that car,' what happened first?"

AA: "You bought the car."

LIDA BAKER: "I bought the car. And later I regretted it. Now let me give you a clearer example of that: 'I stopped smoking' versus 'I stopped to smoke.'"

RS: "Alright ... "

AA: "Ohhh."

RS: "Right, 'I stopped smoking' means 'I don't smoke anymore' and 'I stopped to smoke' means I stopped ... "

AA: "To go smoke a cigarette out on the street."

RS: "It's very tricky."

LIDA BAKER: "That's very tricky and very, very — a pitfall for students. Let's see if we can form some kind of a generalization from this, OK? Basically some verbs must have a gerund after them. Some verbs must have an infinitive after them. And some verbs can have both.

"Of the verbs that can have both a gerund and an infinitive after them, sometimes there is no difference in meaning. But sometimes there is a big difference in meaning, as we just saw in the example of 'I stopped smoking/I stopped to smoke.' So those are the four classes of uses of infinitives and gerunds in object position, alright?"

AA: "How do you learn them?"

LIDA BAKER: "The learner first of all has to know that there is such a thing as a gerund, there is such a thing as an infinitive, that they can occur in subject position, that they can occur following the verb in a variety of positions. So the learner first of all needs consciousness-raising. You know, what are the options?"

RS: "So should a student, once he has that overview, get out a list of words and start memorizing?"

LIDA BAKER: "No, that is not the best way to learn infinitives and gerunds — although, interestingly, when I started teaching many, many, many years ago, typically what textbooks would have would be a list of verbs in alphabetical order. You know, you'd have a list of verbs that are followed by gerunds and a list of verbs that are followed by infinitives. The student would have no choice but just to memorize them.

"Since then, what linguists have learned, or have figured out, is that infinitives and gerunds very often fall into meaning categories. For example, there are a whole bunch of verbs that are generally used with the meaning of communicating something that are all followed by gerunds. I'll give you a couple of examples. To recommend: 'My best friend recommended seeing a doctor.' Or the verb suggest: 'He suggested leaving early in order to avoid the traffic.'

"So, many textbooks nowadays present the verbs which are followed by gerunds versus the verbs that are followed by infinitives in terms of meaning categories, OK? Then there is a category of verbs of choice or intention, that have that meaning, so verbs like choose or decide or refuse. They're followed directly by the infinitive. So: 'He decided to go,' 'He expected to receive a letter from his mother.' The point is that infinitives and gerunds can be learned alphabetically, like you mentioned, but they can also be learned in categories."

AA: Lida Baker writes textbooks for English learners and teaches at the American Language Center at the University of California, Los Angeles. We have the first part of this topic, and all of her previous segments, on our Web site, voanews.com/wordmaster.

RS: And our e-mail address is word@voanews.com. With Avi Arditti, I'm Rosanne Skirble.