The term F-A-C, E.G. can be solved as TRIAD, a five letter word. A TRIAD is a group of three people or things that are closely related. It is commonly used to refer to a group of three musicians who play together, but it can also be used to describe any three people or things that are closely related. In politics, a TRIAD is a group of three countries that have strong ties and often work together. In chemistry, a TRIAD is a group of three elements that have similar properties.