functionary

As nouns the difference between taxonomy and functionary

is that taxonomy is the science or the technique used to make a classification while functionary is a person employed as an official in a bureaucracy (usually corporate or governmental) who holds limited authority and primarily serves to carry out a simple function for which discretion is not required.

As nouns the difference between functionary and pensionary

is that functionary is a person employed as an official in a bureaucracy (usually corporate or governmental) who holds limited authority and primarily serves to carry out a simple function for which discretion is not required while pensionary is one who receives a pension; a pensioner.

As an adjective pensionary is

maintained by a pension; receiving a pension.