From Latin "par" directly:
* Parity: Equality, especially in status or value.
* Parallel: Running or lying side by side, at the same distance apart.
* Paragon: A model of excellence or perfection.
* Pair: Two things that are similar or go together.
* Peer: A person of the same age, status, or ability as another.
* Parallelogram: A quadrilateral with opposite sides parallel.
* Parellelepiped: A prism whose bases are parallelograms.
With additional prefixes and suffixes:
* Imparity: Inequality
* Disparity: A great difference.
* Compare: To examine two things to find similarities and differences.
* Parity check: A method of error detection.
* Reparation: The act of making amends for a wrong.
Other words using related roots:
* Part: A portion or division of something. (Related to the Latin *pars*)
* Partially: Not completely. (Related to the Latin *pars*)
* Particular: Specific or individual. (Related to the Latin *pars*)
It's important to note that the root pari is not commonly used independently, but rather forms part of other words.