# Meaning of prefix p,p′-?

I recently stumbled across the substance "p,p′-terphenyldicarboxylic acid" in a scientific journal when recently reading about metal–organic frameworks.

Could someone explain the prefix p,p'- to me?

• Related to this is the $p,p'$ prefix for DDT, where we have two para chloro substituents on two different phenyl rings. – Gaurang Tandon Jan 10 '18 at 10:57

An unambiguous name would denote both the terphenyl core, as well as the positions of the $\ce{COOH}$ substituents on the outer rings, such as in p-terphenyl-4,4'-dicarboxylic acid.