Fully grasping the difference between perfect and imperfect is often difficult for students whose native language (like English) doesn't have the same distinction. As a result, questions on the subject regularly come up on the forum. The difference is also difficult to explain, even for someone (like me) whose native language has the same distinction. So I thought it might be a good idea to apply myself once and for all to write as good and complete an explanation as I could, and to make it a sticky thread which people with questions on the subject could be redirected to. I will do my best, and I apologize if I fail to be altogether clear on one point or another.
A FEW VERY BASIC AND IMPERFECT (I DIDN'T WANT THE PUN, BUT WHAT OTHER WORD TO USE?) GUIDELINES
The perfect and the imperfect are both past tenses: they are used to describe actions that took place in the past.
The perfect is used for an action that you consider in its entirety, as one block, from its beginning to its end (or, if you don't really "see" the end, you at least "see" the beginning — as in an action that started just then). This action can either still have a more or less tangible result in the present, or not. In the first case, it corresponds to the English present perfect: "I have done this" = "It is now done". In the second case, it corresponds to many situations in which the English preterite is used: "I did this (once in the past)".
The imperfect is used when you are talking about:
1) A certain point during an on-going action in the past. This use is often more or less equivalent to the English past continuous, "I was doing this". You can feel confident that the English past continuous will generally translate to the imperfect in Latin.
2) A certain point of a period during which the action was regularly, habitually repeated. In such situations where in English you could say "At that time, I used to do this" or "Back in the day, I would regularly do this", you will usually find the imperfect in Latin.
But the thing is that, in spite of the above basic guidelines and approximate equivalences, there is no one-to-one equivalence between the Latin perfect and imperfect and English tenses. The exact same distinction is not found in English. The Latin imperfect is also found in some situations where the English preterite is used. Which means that the English preterite can translate to the Latin imperfect as well as to the perfect, depending on context; and this is where things get more complicated, and where I will need to give more complex explanations to try and give you as best an idea as possible of the fundamental difference between the two tenses.
But first, let me mention:
A COUPLE OF FREQUENT MISCONCEPTIONS ABOUT THE TWO TENSES
- Some think that the imperfect is always used for an action that lasted a long time, and the perfect always for an action that lasted a short time. That is not true. Well, since the imperfect is used to describe a "background" action (something that was happening/was the case (when...)), it may be that, statistically, you'll find the imperfect more often in actions that lasted for a relatively long time than in actions that lasted for only one second, but the fundamental nature, the fundamental meaning of the tense, is not about duration. So you'd better discard this idea of duration altogether, because it is bound to mislead you. The perfect is quite often found to describe actions that lasted for one second, but also for hours, days, years, centuries... Definitely, the fundamental distinction between the two tenses is not about duration.
- The term "on-going action" being often used to describe the imperfect, some students misinterpret it as meaning that it is an action continuing into the present. That is not the case. The imperfect is a past tense. The action was "on-going" in the past.
MORE IN DEPTH
First, let us see what "perfect" and "imperfect" actually mean. They come from Latin perfectum and imperfectum, which mean, respectively, "completed/finished" and "not completed/unfinished". So, the perfect represents an action that you visualize in its entirety: you visualize it from its beginning to its end, and you see it completed (or, even if you don't really visualize the end, you visualize at least the beginning); while the imperfect is an action that you visualize at a point after it started and when it wasn't finished yet, but on-going. This does not mean that it is not finished yet and still on-going in the present, but that it was not finished at the moment you are talking about. You don't visualize it entirely from its beginning to its end, but you visualize only a certain point somewhere in the middle of it. The action was probably already going on somewhat before the moment you're talking about, and was perhaps going to go on a bit further.
Let's take two examples.
First: In via ambulabam, cum amico tuo Marco occurri. "I was walking on the street, when I ran into your friend Mark." We have here two verbs, one of which is imperfect, ambulabam, and the other perfect, occurri. How do they differ? I was already walking before this very moment I'm talking about, and it may be that I went on walking just a bit after that. I am not visualizing the whole time during which I walked, from the moment I started to the moment I stopped, but only a certain point "somewhere in the middle of my walking", the moment just before I ran into your friend. At that very moment, the action of walking was not finished, but on-going, even if I stopped walking on the next second. Hence the imperfect. Now, what about occurri? This action I am visualizing in its entirety: I both started and finished running into your friend at the time I'm talking about. I'm not talking about a certain point in the middle of my running into your friend. I see the action in its entirety, as one block. Hence the perfect. The difference feels perhaps relatively obvious in this example due to the fact that here the English makes a distinction too: the past continuous (which, as mentioned earlier, regularly translates to the Latin imperfect), "I was walking", is used for the first verb, while the preterite, "I came", is used for the second. But now let's take a second example where English will make no distinction and use the preterite for both verbs. Exactly the same principle as in the first example will apply in Latin; it may just be less immediately obvious to an English-speaking student because no difference will be marked in the English version of the sentence.
Putabam hoc fieri posse; tu me refutasti. "I thought that this could be done; you proved me wrong." Why is putabam in the imperfect? Because I didn't think it — start thinking it and complete my thought — just then, but it was an opinion I already had somewhat before, and I am talking about a certain moment in the period during which I thought that. Refutasti is in the perfect because this action is visualized in its entirety. You started and finished proving me wrong then. I'm having in mind the whole action of proving me wrong, not a certain point during the process of proving me wrong (which would require the imperfect).
So with the perfect you consider an action in its entirety — no matter the duration of the action; e.g. "He lived a hundred years" will be centum annos vixit (perfect): when you say this, you are considering, from a point of view in the present, the whole time during which he lived, from beginning to end, as one block.
Centum annos vivebat (imperfect) would mean "He had been living for a hundred years (he was still living then, he hadn't quite finished)". If you say this, you are going back mentally to a certain point in the past, a certain point of the period during which he lived, and you are saying that the state of affairs at that moment was that he was living, and had been doing so for a hundred years already. Or in theory, you could also be going back mentally to a certain point in a period during which a human being habitually lived a hundred years. E.g. "Man was stronger in those days; he used to live a hundred years." With the imperfect, you are going back mentally to a certain point in the past, and describing a state of affairs, something that was on-going at that time.
Now let's take a couple of examples where, in Latin, either the perfect or the imperfect could be used depending on context, with a somewhat different meaning, even though both versions could translate the same way into English, and let me try to give you an idea of how they differ.
1) Rex magnus hac in terra regnavit. (Perfect)
2) Rex magnus hac in terra regnabat. (Imperfect)
"A great king reigned in this land."
In 1), I am mentioning the king's reign as an event that happened once. I have his whole reign in mind. I see it completed, in its entirety, from a point of view in the present. In 2), I am saying that, at a certain time which I have in mind, one of the things that were going on was that a great king reigned here. I am having in mind some point during his reign. You could say this when setting the background to a story you're telling ("At the time of the protagonist's birth, a great king reigned in this land, the kingdom was in peace, and the people were happy (such was the state of affairs at this point). But one day...") or in any context where you're having a certain time in mind that was at some point in his reign; either because that time been mentioned (- Do you remember year N? - Yes. Ah! A great king reigned in this land then! (He already reigned before year N, and perhaps went on reigning afterwards, but in year N, his reign was on-going.)) or implied in the context — generally speaking, because you're going back mentally to that time for whatever reason.
1) Scribere ad te volebam. (Imperfect)
2) Scribere ad te volui. (Perfect)
"I wanted to write to you."
1) means that I was in a state of desire to write to you. 2) means that the desire to write to you came to me then.
1) Illo tempore saepe pugnabam. (Imperfect)
2) Illo tempore saepe pugnavi. (Perfect)
"At that time, I often fought." (1) could also translate to "At that time, I would often fight" or "At that time, I used to fight often".)
In 1) I am, again, going back mentally to some point of that period during which I often fought, and visualizing it at some point in the middle. In 2), I am considering the whole period during which I often fought in its entirety, as if it were in some way one event: my "fighting career" is viewed here in its entirety like the reign of the king in rex magnus hac in terra regnavit.
Finally, let me come back to the near-equivalence of English past continuous and Latin imperfect to point out something concerning this: some English verbs are less often found in the continuous tenses than others are, and some almost never (e.g. you hardly ever say "I was knowing"). This does not at all mean that they are similarly less often found in the imperfect in Latin. This regularly causes students to misuse the perfect where they needed the imperfect. Such verbs include (but are not limited to; these are just those I can think of now): to be, to know, to want, to think, to believe. So when you need to use the Latin equivalent of one of these verbs (or a similar one) in past tense, be particularly careful* about whether it is, in the context, describing an on-going state (= Latin imperfect) or a "one-block" event (= Latin perfect). E.g. You need to say "I knew" in Latin. Do you mean: 1) that you were in a state of knowing — e.g."I knew she would do this, and indeed she did" — , 2) that the knowledge came to you just then — e.g. "When I saw him, I knew he was your father" — or 3) are you considering a whole, more or less definite period during which you knew, from its beginning to its end — e.g. "I knew his name for a long time, but then I forgot"? If the answer is 1), you need the imperfect. If it's 2) or 3), you need the perfect. You can perhaps also try substituting the English verb in question with another verb that doesn't have this peculiarity of being rarely found in the continuous tenses; for example "to run", "to eat" or "to watch TV", and see if it would work in the past continuous (was/were [verb]ing) in your context or not. If it does, you probably need the imperfect.
*I don't mean that you shouldn't be careful in other situations as well. Of course you should in fact always be careful.
I hope this post has clarified things at least a bit for you. If you still have questions, you can post them on the forum, and we'll answer them if possible.
A FEW VERY BASIC AND IMPERFECT (I DIDN'T WANT THE PUN, BUT WHAT OTHER WORD TO USE?) GUIDELINES
The perfect and the imperfect are both past tenses: they are used to describe actions that took place in the past.
The perfect is used for an action that you consider in its entirety, as one block, from its beginning to its end (or, if you don't really "see" the end, you at least "see" the beginning — as in an action that started just then). This action can either still have a more or less tangible result in the present, or not. In the first case, it corresponds to the English present perfect: "I have done this" = "It is now done". In the second case, it corresponds to many situations in which the English preterite is used: "I did this (once in the past)".
The imperfect is used when you are talking about:
1) A certain point during an on-going action in the past. This use is often more or less equivalent to the English past continuous, "I was doing this". You can feel confident that the English past continuous will generally translate to the imperfect in Latin.
2) A certain point of a period during which the action was regularly, habitually repeated. In such situations where in English you could say "At that time, I used to do this" or "Back in the day, I would regularly do this", you will usually find the imperfect in Latin.
But the thing is that, in spite of the above basic guidelines and approximate equivalences, there is no one-to-one equivalence between the Latin perfect and imperfect and English tenses. The exact same distinction is not found in English. The Latin imperfect is also found in some situations where the English preterite is used. Which means that the English preterite can translate to the Latin imperfect as well as to the perfect, depending on context; and this is where things get more complicated, and where I will need to give more complex explanations to try and give you as best an idea as possible of the fundamental difference between the two tenses.
But first, let me mention:
A COUPLE OF FREQUENT MISCONCEPTIONS ABOUT THE TWO TENSES
- Some think that the imperfect is always used for an action that lasted a long time, and the perfect always for an action that lasted a short time. That is not true. Well, since the imperfect is used to describe a "background" action (something that was happening/was the case (when...)), it may be that, statistically, you'll find the imperfect more often in actions that lasted for a relatively long time than in actions that lasted for only one second, but the fundamental nature, the fundamental meaning of the tense, is not about duration. So you'd better discard this idea of duration altogether, because it is bound to mislead you. The perfect is quite often found to describe actions that lasted for one second, but also for hours, days, years, centuries... Definitely, the fundamental distinction between the two tenses is not about duration.
- The term "on-going action" being often used to describe the imperfect, some students misinterpret it as meaning that it is an action continuing into the present. That is not the case. The imperfect is a past tense. The action was "on-going" in the past.
MORE IN DEPTH
First, let us see what "perfect" and "imperfect" actually mean. They come from Latin perfectum and imperfectum, which mean, respectively, "completed/finished" and "not completed/unfinished". So, the perfect represents an action that you visualize in its entirety: you visualize it from its beginning to its end, and you see it completed (or, even if you don't really visualize the end, you visualize at least the beginning); while the imperfect is an action that you visualize at a point after it started and when it wasn't finished yet, but on-going. This does not mean that it is not finished yet and still on-going in the present, but that it was not finished at the moment you are talking about. You don't visualize it entirely from its beginning to its end, but you visualize only a certain point somewhere in the middle of it. The action was probably already going on somewhat before the moment you're talking about, and was perhaps going to go on a bit further.
Let's take two examples.
First: In via ambulabam, cum amico tuo Marco occurri. "I was walking on the street, when I ran into your friend Mark." We have here two verbs, one of which is imperfect, ambulabam, and the other perfect, occurri. How do they differ? I was already walking before this very moment I'm talking about, and it may be that I went on walking just a bit after that. I am not visualizing the whole time during which I walked, from the moment I started to the moment I stopped, but only a certain point "somewhere in the middle of my walking", the moment just before I ran into your friend. At that very moment, the action of walking was not finished, but on-going, even if I stopped walking on the next second. Hence the imperfect. Now, what about occurri? This action I am visualizing in its entirety: I both started and finished running into your friend at the time I'm talking about. I'm not talking about a certain point in the middle of my running into your friend. I see the action in its entirety, as one block. Hence the perfect. The difference feels perhaps relatively obvious in this example due to the fact that here the English makes a distinction too: the past continuous (which, as mentioned earlier, regularly translates to the Latin imperfect), "I was walking", is used for the first verb, while the preterite, "I came", is used for the second. But now let's take a second example where English will make no distinction and use the preterite for both verbs. Exactly the same principle as in the first example will apply in Latin; it may just be less immediately obvious to an English-speaking student because no difference will be marked in the English version of the sentence.
Putabam hoc fieri posse; tu me refutasti. "I thought that this could be done; you proved me wrong." Why is putabam in the imperfect? Because I didn't think it — start thinking it and complete my thought — just then, but it was an opinion I already had somewhat before, and I am talking about a certain moment in the period during which I thought that. Refutasti is in the perfect because this action is visualized in its entirety. You started and finished proving me wrong then. I'm having in mind the whole action of proving me wrong, not a certain point during the process of proving me wrong (which would require the imperfect).
So with the perfect you consider an action in its entirety — no matter the duration of the action; e.g. "He lived a hundred years" will be centum annos vixit (perfect): when you say this, you are considering, from a point of view in the present, the whole time during which he lived, from beginning to end, as one block.
Centum annos vivebat (imperfect) would mean "He had been living for a hundred years (he was still living then, he hadn't quite finished)". If you say this, you are going back mentally to a certain point in the past, a certain point of the period during which he lived, and you are saying that the state of affairs at that moment was that he was living, and had been doing so for a hundred years already. Or in theory, you could also be going back mentally to a certain point in a period during which a human being habitually lived a hundred years. E.g. "Man was stronger in those days; he used to live a hundred years." With the imperfect, you are going back mentally to a certain point in the past, and describing a state of affairs, something that was on-going at that time.
Now let's take a couple of examples where, in Latin, either the perfect or the imperfect could be used depending on context, with a somewhat different meaning, even though both versions could translate the same way into English, and let me try to give you an idea of how they differ.
1) Rex magnus hac in terra regnavit. (Perfect)
2) Rex magnus hac in terra regnabat. (Imperfect)
"A great king reigned in this land."
In 1), I am mentioning the king's reign as an event that happened once. I have his whole reign in mind. I see it completed, in its entirety, from a point of view in the present. In 2), I am saying that, at a certain time which I have in mind, one of the things that were going on was that a great king reigned here. I am having in mind some point during his reign. You could say this when setting the background to a story you're telling ("At the time of the protagonist's birth, a great king reigned in this land, the kingdom was in peace, and the people were happy (such was the state of affairs at this point). But one day...") or in any context where you're having a certain time in mind that was at some point in his reign; either because that time been mentioned (- Do you remember year N? - Yes. Ah! A great king reigned in this land then! (He already reigned before year N, and perhaps went on reigning afterwards, but in year N, his reign was on-going.)) or implied in the context — generally speaking, because you're going back mentally to that time for whatever reason.
1) Scribere ad te volebam. (Imperfect)
2) Scribere ad te volui. (Perfect)
"I wanted to write to you."
1) means that I was in a state of desire to write to you. 2) means that the desire to write to you came to me then.
1) Illo tempore saepe pugnabam. (Imperfect)
2) Illo tempore saepe pugnavi. (Perfect)
"At that time, I often fought." (1) could also translate to "At that time, I would often fight" or "At that time, I used to fight often".)
In 1) I am, again, going back mentally to some point of that period during which I often fought, and visualizing it at some point in the middle. In 2), I am considering the whole period during which I often fought in its entirety, as if it were in some way one event: my "fighting career" is viewed here in its entirety like the reign of the king in rex magnus hac in terra regnavit.
Finally, let me come back to the near-equivalence of English past continuous and Latin imperfect to point out something concerning this: some English verbs are less often found in the continuous tenses than others are, and some almost never (e.g. you hardly ever say "I was knowing"). This does not at all mean that they are similarly less often found in the imperfect in Latin. This regularly causes students to misuse the perfect where they needed the imperfect. Such verbs include (but are not limited to; these are just those I can think of now): to be, to know, to want, to think, to believe. So when you need to use the Latin equivalent of one of these verbs (or a similar one) in past tense, be particularly careful* about whether it is, in the context, describing an on-going state (= Latin imperfect) or a "one-block" event (= Latin perfect). E.g. You need to say "I knew" in Latin. Do you mean: 1) that you were in a state of knowing — e.g."I knew she would do this, and indeed she did" — , 2) that the knowledge came to you just then — e.g. "When I saw him, I knew he was your father" — or 3) are you considering a whole, more or less definite period during which you knew, from its beginning to its end — e.g. "I knew his name for a long time, but then I forgot"? If the answer is 1), you need the imperfect. If it's 2) or 3), you need the perfect. You can perhaps also try substituting the English verb in question with another verb that doesn't have this peculiarity of being rarely found in the continuous tenses; for example "to run", "to eat" or "to watch TV", and see if it would work in the past continuous (was/were [verb]ing) in your context or not. If it does, you probably need the imperfect.
*I don't mean that you shouldn't be careful in other situations as well. Of course you should in fact always be careful.
I hope this post has clarified things at least a bit for you. If you still have questions, you can post them on the forum, and we'll answer them if possible.
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