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?
I am guessing that this is the compound you are interested in:

Sigma labels this compound as p-Terphenyl-4,4′′-dicarboxylic acid (or 1,4-Bis(4-carboxyphenyl)benzene).

In your case, the p,p' indicates that the 2 carboxylic acids are in the para positions on 2 of the phenyl rings.