I received my passport, and where you sign your name do you spell out your middle name or is it OK to just put your middle initial? Does it matter either way?

It is not an issue. If you normally use your middle initial, do the same for your passport.

It's a "signature", so it should be your standard signature. If they want to verify your the person in the passport, they may ask you to sign your name on a piece of paper (or look at your driver license, etc.) and compare the signatures. If you never spell out your middle name, then don't spell it out on the passport signature.

I agree you should sign it like you usually write your name. My passport shows my full middle name which I never use. My signature on the passport is my first and last name only (as I'd usually write it on a check or form). It has never been questioned.

Thanks, that clears things up for me.

I have a problem regarding passport my passport having my married name but my signature is having my father name initial so is it matter and creates any problem

Neha: Do you mean you signed your passport with a different name?

You don't say what nationality you are . . . But in general one's passport must match the ticket name. And info on a passport must be correct/consistent.