Editor's note: This is the third episode of four-part series on verb tenses. Be sure to listen to part one and part two first.

For VOA Learning English, this is Everyday Grammar.

Today we are going to talk about the perfect verb tenses. Perfect tenses generally focus on how a past action affects the present.For example, "I have already eaten." The suggestion is that the speaker is not hungry.

Perfect verb tenses are the most difficult for English learners. The term "perfect" can be confusing. What does grammar have to do with not making mistakes? When you are talking about grammar, perfect has a different meaning. It comes from the Latin word perfectum, which means "complete."

The most important thing to remember is the perfect tenses always refer to completed actions. If you get confused, try replacing "perfect" with "completed" and the time relationship should become clearer.

PERFECT

TENSES

It had already snowed before I left.

Had + past participle verb

I have driven in snow many times.

Have/has + past participle verb

It will have snowed 6 inches by the end of the day.

Will have + past participle verb

Present perfect

We will start with the present perfect. You form the present perfect using has or have followed by a past participle verb. For example, "I have seen Star Wars."

The use of the present perfect here gives us three pieces of information. First, it tells us that the event is finished. Second, it tells us that the exact time of the action is unknown or unimportant. Third, it suggests that the experience of seeing Star Wars has some effect in the present.

One of the most difficult distinctions for English learners to make is the difference between the simple past and present perfect.

Remember, when there is a specific time, you use the simple past. In the sentence "I saw Star Wars last night," the adverb last night is a specific time.

You cannot say "I have seen Star Wars last night." But, you could say, "I have seen Star Wars before" or "in the past" or "three times."

You should also use the present perfect to refer to a repeated action in the past. For example, "I have taken that test four times." The exact time of each action is not important.

You can also use the present perfect to describe an action that did not happen, using the adverb never. "I have never traveled outside of my country" and "I have never smoked in my entire life." Something that did not happen the past, like not traveling and not smoking, can also have an effect in the present.

The adverbs never, already, yet and so far are common in the present perfect. Adverbs are often the best indicators of which verb tense to use.

Past Perfect

Now let us look at the past perfect. The past perfect describes an activity that was finished before another event in the past. For example, "She had already had a baby before she graduated."

To form the past perfect, use had followed by a past participle verb. For the second action, use before or by the time followed by the simple past verb. Imagine you were at a New Year's Eve party, but you fell asleep before midnight. You could say, "I had already fallen asleep before the New Year came."

You can use the past perfect to talk about how an experience from the distant past relates to an experience from the more recent past. For example, "The soldier wasn't scared because he had already been in battle before."

In other words, battle was not a new experience for the soldier.

If the time relationship is clear, you can choose between the past perfect and the simple past. "My grandfather passed away before I was born," has the same meaning as "My grandfather had passed away before I was born."

The past perfect just emphasizes that the first action was completed before the second action.

Future perfect

Let us move on to the future perfect. Use the future perfect when you know that one future action will be completed before another future action. For example, "I will have graduated from college before my little brother graduates from high school."

The future perfect has very limited use because we rarely know a future sequence of events with any certainty. When it is used, the future perfect usually refers to major life events that are planned years in advance.

And those are the three perfect tenses. Join us next week on Everyday Grammar for an explanation of the perfect progressive tenses.

I'm John Russell.

And I'm Ashley Thompson.

Adam Brock wrote this story for Learning English. Jill Robbins and Kathleen Struck were the editors.

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participle - grammar. a form of a verb that is used to indicate a past or present action and that can also be used like an adjective

adverb - grammar. a word that describes a verb, an adjective, another adverb, or a sentence and that is often used to show time, manner, place, or degree

indicator - n. a sign that shows the condition or existence of something

scared - adj. afraid of something