Triad (noun)

1. A group or set of three people or things.
2. A combination of three elements or components.
3. A group or combination of three similar or related elements or components.

Origin:

Mid 17th century: from greek trias, triad-, from tri- "three".

Examples:

1. The triad of democracy, capitalism, and freedom is often touted as the cornerstone of western society.
2. The musical triad of bass, guitar, and drums is considered the foundation of rock music.
3. In Chinese mythology, the triad of heaven, earth, and man is considered crucial to the balance of the universe.
4. The triad of education, hard work, and determination is said to lead to success.
5. The three-color triad of red, blue, and yellow is considered the basic palette for artists.