Whether it’s birds, opera singers, aces, or golfers, you can use the word trio to refer to anything made up of three.
You can probably tell by tri– that trio involves three of something. It’s often used to describe a musical arrangement featuring three vocal parts or three different instruments, or a musical group made up of three players, such as a jazz trio consisting of a piano player, a bass player, and a drummer. For those not musically inclined, the word can be used more broadly to refer to three of anything, such as a trio of friends.
Source : vocabulary.com
In response to The Daily Post’s weekly photo challenge : Trio