To complete the following sentence with a suitable form of the verb in bracket, I used past perfect (hadn't come),** but the answer key says the correct tense is past simple (didn't come).**

I cannot understand why. Can you provide me with an explanation, please?

" If you ___________ to class yesterday, you won't know about the exam. "

  • As written the sentence makes no sense. There's no way to match up the conditional with the simple future won't. "Didn't come" is no better than "hadn't come". Is this from a source written by a native speaker?
    – Andrew
    Jan 4, 2019 at 16:36
  • @Andrew - I disagree that the sentence doesn't make sense. It makes sense if it's addressed to the "impersonal you" as a general principle (not to the specific "you" of the listener). It has the same construction as "If you didn't buy a ticket, you won't win the lottery." Jan 4, 2019 at 16:51
  • @Andrew - It's from "New English File" published by Oxford. Advanced level.
    – M.N
    Jan 4, 2019 at 17:00
  • @CanadianYankee Do people really say that, though? I would have said, "If you didn't buy a ticket, how can you expect to win?" Either that or I would use the present tense: "If you don't buy a ticket, you won't win". Mixing up tenses like that seems very awkward.
    – Andrew
    Jan 4, 2019 at 17:18
  • @CanadianYankee Although I see how the writer might want to express a causal relationship -- in which case I would use "since": "Since you didn't go to class yesterday, you won't know about the exam".
    – Andrew
    Jan 4, 2019 at 17:25

3 Answers 3


If you didn't come to class yesterday, you won't know about the exam.

All the modal verbs have various meanings in various contexts, and the variety of conditional constructions is much greater than is usually taught; so without context a sentence like this offers many opportunities for confusion. You have to sort of work your way back from the forms to the implied context for it to make sense.

  1. One very reliable "rule" for conditional constructions is that both the condition clause (the subordinate if clause or protasis) and the consequence clause (the main then clause or apodosis) must express the same order of "reality": that is, both must be either real or unreal. In this case won't know is unambiguously real (the unreal form would be wouldn't know), so didn't go must be real as well.

    Note that this excludes If you hadn't gone ..., since that always implies a "condition contrary to fact"—an unreal condition.

  2. Another consideration here is that will (or, as here, won't) has other meanings than just marking future tense. There's a pretty strong indication that you won't know ... is a simple prediction: obviously you will know something about the exam from the very fact that I'm mentioning it! The likeliest meaning here is the "deictic" sense of will: a fairly certain present-tense inference that such-and-such is a fact, as in

    A: Who's that at the door?
    B: Oh, that will be John—he said he was coming over.

  3. There are other considerations in play here, such as the difference between "actualization" and "inference" conditionals (this is an "inference" conditional, in which the condition can actually follow its consequence) and the distinction between "open" and "closed" conditions (this is a "closed" condition, one which is accepted as true), but you don't really need these to understand this sentence. To paraphrase it:

    Since (I noticed or you tell me that) you didn't come to class yesterday, I assume you don't know about the exam. which implies, one hopes, that the speaker will continue Let me tell you what you need to know.


The correct form is

"If you didn't go to class yesterday, you wouldn't know about the exam."

However, especially in speech, even native speakers can be casual about sequence of tenses so you may well hear

"If you didn't go to class yesterday, you don't/won't/can't know about the exam."

American English is in flux about conditionals and subjunctives.

  • Is this a particularly AmEng phenomenon?
    – Tashus
    Jan 4, 2019 at 17:52
  • I am not very conversant with English outside the US. What I can say is that in the US the traditional rules of formal English with respect to conditionals, subjunctives, and sequence of tenses are frequently no longer followed. Jan 4, 2019 at 18:53
  • I would find this use of didn't go as implicitly unreal bizarre: grammatically defensible, perhaps, but not idiomatic in any register. Jan 4, 2019 at 19:19
  • @StoneyB I did not say that I would use it or that I find it attractive. I said that formations like this are common in the US, even among educated people. I know: they grate on my ear all too frequently. Jan 5, 2019 at 0:18
  • I was speaking of what you offer as the "correct" version. Jan 5, 2019 at 0:46

I came across the following point while I was studying the IF section in Michael Swan’s Practical English Usage. I think it will help us all.

If: ordinary structures

When we are not talking about ‘unreal’ situations, we use the same tenses with if as with other conjunctions. Present tenses are used to refer to the present, past tenses to the past, and so on. Compare:

If you didn’t study physics at school, you won’t understand this book.

Because you didn't study physics at school, you won’t understand this book.

I believe this further clarifies what has been discussed here. Am I right?

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