The word "nonfunctioning" refers to things that are not working or operating properly. Some antonyms for this word include "functioning," "working," "operating," "active," "live," and "viable." These words can be used to describe things that are in good working condition, such as machines, equipment, and appliances. They can also be used to describe people who are healthy and capable of performing their duties or responsibilities. When writing or speaking, it is important to use the correct antonyms for the word "nonfunctioning" depending on the context and the message being conveyed.