英语单词大师：Present Perfect Tense

 AA: I'm Avi Arditti with Rosanne Skirble, and this week on Wordmaster: practice makes perfect.

RS: With us from Los Angeles is English teacher Lida Baker 1 to explain a part of grammar that makes English learners tense.
AA: It's the verb tense known as the present perfect. First of all, Lida says don't be misled by the archaic 2 meaning of perfect.
LIDA BAKER: "In Latin it has to do with whether something is complete or incomplete 3. In linguistic 4 terms, the present perfect tense is pretty unique, pretty unusual, and it's something that students always wrestle 5 with. So the present perfect tense is formed by using the auxiliary 6 verb 'have' and the past participle of a verb. And if that terminology 7 is a little bit too confusing, I'll just give you some simple examples: 'I have eaten breakfast already' or 'he has seen that movie three times.' So the present perfect is that form that uses either have or has, followed by the past participle form of the verb."RS: "That's the form. Now we need to focus on how you use it."LB: "Well, that's the interesting part. One of the basic meanings of the present perfect tense is to talk about things that began in the past and continue up to the moment of speaking. An example of that would be something like 'I have lived in Los Angeles for 25 years,' 'she's been a teacher since she was 25 years old.' So cases where the action began in the past and continues until this moment, that's one way in which we use the present perfect tense.
"Cases like that do not give students difficulty, though. Maybe it's because with that meaning we often pair the sentence with a phrase that starts with 'for' or 'since.' So, 'for 16 years' or 'since I was 12 years old,' those sorts of things are not hard for students to learn.
"We use the past tense when something occurred in the past and we know exactly when it happened. So, 'I visited my grandmother three days ago' or 'he graduated from college last month.' When the time that the event occurred is given, then according to the rules, we have to use the past tense, OK?
"In contrast to that, if something occurred in the past but there is no specific time stated, that's when we use the present perfect. So we would say something like 'I have finished my homework,' 'I've seen that movie' and so on. And, according to the strict rules of grammar, if you take a sentence like 'I've seen that movie' and you use it with the word 'yesterday,' in American English strictly 8 speaking that sentence is incorrect. It would be wrong to say 'I have seen that movie yesterday.' But in reality -- "RS: "Instead you would say 'I saw that movie yesterday.'"LB: "That's right."AA: "Now, like in the homework example, if a kid comes up to you and says 'I have -- I've finished my homework,' they're talking about like in the past few minutes as opposed to 'I finished my homework -- "RS: "Two days ago."AA: " -- two days ago,' or something like that, is that what you're ... "LB: "That could be one explanation. But another explanation could be that the student is handing me his paper, you see. So this is how the relevance 9 to the present is established. He says, 'I've finished my homework, and here it is.' You see? Sometimes the link is established by means of the context 10, OK? Sometimes we've had some kind of an experience in the past that has relevance for the present, in a sentence something like, 'I've used that machine lots of times, so I can teach you or help you with it now.'
"Another way that this relevance to the current moment is established is if something has happened in the past, but there's a good probability 11 that it might happen again. So a sentence like, 'I've been to the Hollywood Bowl twice this summer.' The Hollywood Bowl is a large outdoor concert arena 12 here in Los Angeles. So, 'I've been to the Hollywood Bowl twice this summer ... '"RS: And the use of the present perfect indicates she might go again -- although at the present moment, Lida is busy with a new group of students.
AA: Lida Baker teaches in the American Language Center at the University of California, Los Angeles. All her previous lessons with us are on our Web site, voanews.com/wordmaster.
RS: And if you'd like to send Avi and me an e-mail, the address is word@voanews.com. With Avi Arditti, I'm Rosanne Skirble.