triplet

noun

• 1 (usually triplets) one of three children or animals born at the same birth.

• 2a set or succession of three similar things.
• Music a group of three equal notes to be performed in the time of two or four.
• a set of three rhyming lines of verse.

• 3 Physics & Chemistry an atomic or molecular state characterized by two unpaired electrons with parallel spins.
• a group of three associated lines close together in a spectrum or electrophoretic gel.