An engineering thermoplastic polymer, polyphenylene sulfide

• Used for high-heat, chemical-resistant parts

In UK politics, an unpaid aide to a minister

• Liaises between minister and backbench MPs

A second note after the postscript in a letter or email

• Written as an additional afterthought

In medicine, inflammation after surgical opening of the pericardium

• Causes fever, chest pain, and effusion

Plural of PP, especially prepositional phrase in linguistics

• Used to refer to multiple PP constituents