Question

What is a Principal Petitioner?

Answer 1

If the principal applicant has already immigrated to the US and is a legal permanent resident (LPR) when the petitioner dies, the derivative applicants (usually the children of the principal applicant) are generally still eligible to apply for an immigrant visa.

Answer 2

Principle petitioner or principal applicant is the person who is named in a petition.

So for example, if an American citizen has filed a petition for his married daughter for immigrating to the United States of America then the daughter will be known as the principal applicant.

The family member wi be getting a visa for her position.

A derivative status is hence obtained in this manner.