The use of the English tenses in a nutshell

http://www.unc.edu/depts/wcweb/hando...ditionals.html


http://answers.yahoo.com/question/in...9024332AA9s2zg
"Best Answer - Chosen by Asker

In your example sentence it should be "If he were (was) a dog, he would jump..."

There are, more or less, four types of if sentences, and after if you can have present, past or past perfect.

1st conditional/real conditional:
If + present, future (will/going to)

If it rains tomorrow, I'll stay at home.

This is used with real possibilities in the future.

2nd conditional/unreal conditional
If + past (with "to be" were/was are both typical), would/could + verb

If I were/was a bird, I could fly high in the sky
If it snowed in August, I would be very surprised.

This is used for situations which are either impossible (If I were a bird) or very unlikely (if it snowed in August)

3rd conditional/past conditional
If + past perfect, would have + verb.

If I hadn't broken my leg, I could have become a professional footballer.
If I had known that you were coming, I'd have baked a cake.

This is used for if sentences about the past.


0 conditional
If + simple present, simple present.

If you heat water it boils.
If the cat pees on the carpet, it means her cat-toilet is not clean.

This is used to expressed scientific truths, things that are always true.
Source(s):

Any English grammar book from the past fifty years.
(oh, and I teach English as a Foreign Language)"