noun

• A set of three, particularly
• (music) A group of three notes played or written where two notes would ordinarily be; a form of tuplet.
• (physics) A triquark.
• (physics) A quantum state with three allowed projections for the spin.
• A constructed gem consisting of a thin slice of natural opal sandwiched between a clear glass or quartz top and a synthetic or stone backing that enhances the colour of the opal.
• One of a group of three, particularly
• One of a group of three siblings born at the same time to the same mother.
• A surname.