functioning

noun

The way in which a machine or other thing performs or functions: behavior, operation, performance, reaction, working (often used in plural). See action/inaction, machine.

adjective

In action or full operation: active, alive, going, operating, operative, running, working. See action/inaction, awareness/unawareness.

The noun has one meaning:

Meaning #1: process or manner of functioning or operating
  Synonyms: operation, performance

The adjective functioning has one meaning:

Meaning #1: performing or able to perform its regular function
  Antonym: malfunctioning (meaning #1)