Look at this sentence:
He's coming to see us if he has time.
QUESTION: Is he coming to see us?
ANSWER: We don't know. Perhaps he will have time or perhaps he will not have time.
Now look at this sentence: He would be here now if he had the time.
QUESTION: Is he here now?
ANSWER: No, because he doesn't have time.
We usually begin conditions with if.
If it rains tomorrow, I'll stay in.
If Maria is coming to the party, you can tell her the news.
But she won't be able to come if she's in Winnipeg now.
I'm sure she'll come if John has remembered to tell her.
If they saw each other last night, she must know about it.
NOTICE: We cannot use will for future time in a condition: We say
If it rains tomorrow NOT if it will rain
If she's coming NOT if she will be coming
NOTICE: We sometimes use unless (if...not) at the beginning of a condition:
Unless it rains tomorrow, I'll go to the beach.
Unless she's in Winnipeg, I'm sure she'll come.
I'm sure she'll come unless John has forgotten to tell her about it.
If Maria was coming, you could tell her the news.
(But she isn't coming; you can't tell her.)
I would have more money if I didn't smoke.
(But I smoke; I have less money.)
I'd phone him if only I could find his number.
(But I can't find it; I can't phone him.)
If I found a lot of money, I'd give it to the police.
(I don't expect to find any; I'm imagining.)
NOTICE: Would you mind if I left early?
Would + mind + UNREAL CONDITION is a polite way to ask for permission.
If Maria had come, you could have told her the news.
(But she didn't come; you couldn't tell her.)
I'd have phoned him if only I could have found his number.
(But I couldn't find it; I didn't phone.)
If I had found that money, I would have given it to the police.
(I didn't find it; I'm just imagining.)
I'm sure Maria would've come if John hadn't forgotten to tell her.
(But John forgot; she didn't come.)
In this sentence:
If they saw each other, I'm sure they talked about it
the condition is real (talking about past time).
But in this sentence:
If they saw each other, they would talk about it
the condition is unreal (talking about future time).
NOTICE: Conditions can go before the basic sentence, If it's fine, I'll go to the beach, or after it, I'll go to the beach if it's fine. If we put the condition before the basic sentence, we use a comma.