What is the difference between first conditional and second conditional? 1) if i know her, I will tell you 2)If i knew her, i would tell you

how somebody can use the second conditional at the time of speaking when the if clause is in past tense which means it happened earlier?

Sometimes to me, it seems that second conditional is equal to third conditional? somebody please tell me the difference. I searched many websites but didn't find a reply which satisfies me.

3 Answers 3


I shamelessly checked your history here at stack exchange and I determined that you have a problem with conditionals. I type your sentences here and interpret them.

1) If I know her, I will tell you. Imagine a meeting. Somebody is soon going to come to stage and start singing. There is a possibility that he/she might be someone you know.

A: I wonder who is going to sing? Someone you know?

B: If I know her, I will tell you. (He/She hasn't come to stage yet. He/She is going to come to stage).

Now check your second sentence.

2)If I knew her, I would tell you.

Imagine he/she came to the stage and sang and finished. Your friend asks;

A) So, Do you know her?

B) If I knew her, I would tell you. (You don't know her -now-. So you didn't tell).

While your first sentence is referring to future, your second sentence is referring to present.


Wouldn't both sentences mean the same thing - that you don't know her, and therefore, there is nothing to tell in either case? I don't think the tense matters in your example, or for that matter, the conditional. It would be more usual to say something like: I don't know her, and therefore, can't tell you anything [about her]. I am assuming this is what you want to say.

  • Could you explain the difference between these two? If i get promoted, I will give you a treat and If i got promoted, I would give you a treat
    – Joann
    Commented Feb 16, 2016 at 6:27

Obviously you don't know subjunctive forms. Normally a past tense after if/as if is a past subjunctive describing something unreal and not referring to a past event, but to now or the future time.

The asterisk stands for subjunctive form:

  • If only father were* here. - It is a wish, father is not here, she only wishes that her father were* here now.

  • If I had* a million dollars, I wouldn't work any longer. - He doesn't have a million dollars, it is an unreal wish referring to now or later.

In English past indicative and past subjunctive have the same form (except were*). That is a certain difficulty for native speakers, but especially for learners. There are several languages where the forms are differentiated, eg German er hatte (he had) and wenn er hätte (if he had*). So Germans or French people or Italians have a better feeling for unreal past.

Here's a conjugation table with all verb forms for to be and to have, and you can choose any other verb:



  • Thank you, could you tell me more about subjunctive?
    – Joann
    Commented Feb 16, 2016 at 13:17
  • @Johann - Oh, it would be a little booklet, even though some native speakers say English has no subjunctive. And sometimes I get into discussions with natives speakers as to some verb formes are subjunctive or not as it sometimes is really difficult to decide what is what.
    – rogermue
    Commented Feb 16, 2016 at 13:41
  • "it would be a little booklet" Why you used would there? is it possible to use will there. if you could tell me that, it would become a great help for me.
    – Joann
    Commented Feb 16, 2016 at 13:49
  • @Johann - I have used "would" because I have not the intention to write this booklet here. Simply no time. Nevertheless it is a good idea. Should note it down in my list "Booklets to be be written".
    – rogermue
    Commented Feb 16, 2016 at 13:52

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