Resolved questions
both "مهمانی" and "میهمانی" mean "party"? what is the difference between them?

hi
there is no diffrence between them, both of them are equal. In fact both of them are one word which means Party in English.
میهمانی usually uses in written context and is more formal.
مهمانی usually uses is speaking so ي after م removed.
don`t worry this is not very unusuall, you can use both of them.