A more thorough explanation:

Definition: P.P. is an abbreviation that can have two meanings:

1. PER PROCURATIONEM: This Latin phrase means "by agency" or "by proxy." It is used when someone is signing a document on behalf of someone else. For example, if a lawyer signs a contract for their client, they may write "John Smith, p.p. Jane Smith" to indicate that they are signing on Jane's behalf.
2. PROPRIA PERSONA: This Latin phrase means "in one's own person" or "in person." It is used when someone is signing a document for themselves. For example, if you sign a letter to a friend, you may write "Sincerely, p.p. Your Name" to indicate that you are signing the letter yourself.

In the context of patent applications, P.P. can also stand for:

1. Provisional Application: This is a type of patent application that allows inventors to establish an early filing date for their invention. It is not a full patent application and does not require a formal patent claim.
2. Plant Patent Act: This is a U.S. law that allows inventors to obtain patents for new varieties of plants that they have created or discovered.

For example, if an inventor files a provisional patent application for their new invention, they may write "P.P. 12345678" on the application to indicate that it is a provisional application. If they file a patent application for a new plant variety, they may write "P.P.A." on the application to indicate that it is covered by the Plant Patent Act.