The structure of SECOND CONDITIONAL

Like a first conditional, a second conditional sentence consists of two clauses, an "if" clause and a main clause:

if clause	main clause
If I had a million dollars,	I would buy a big house.

If the "if" clause comes first, a comma is usually used. If the "if" clause comes second, there is no need for a comma:

main clause	if clause
I would buy a big house	if I had a million dollars.

We use different verb forms in each part of a second conditional:

if clause	if + subject + simple past verb*
main clause	subject + would + verb

*Note that this "simple past" form is slightly different from usual in the case of the verb BE. Whatever the subject, the verb form is "were", not "was": If I were rich, I'd buy a big house.

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Using the second conditional

The second conditional is used to talk about things which are unreal (not true or not possible) in the present or the future -- things which don't or won't happen:

Example	Explanation
If I were you, I would drive more carefully in the rain.	I am not you -- this is unreal.
Paula would be sad if Jan left.	Jan will not leave -- that's not going to happen.
If dogs had wings, they would be able to fly.	Dogs don't have wings -- that's impossible.