tris-

Meanings

1. A variant of tri- used to indicate that the component that does not take the prefix occurs three times in the compound: trisphosphuret of copper is PCu₃; trisbenzeneazoresorcinol, C₆H(OH)₂(N₂Ph)₃.
2. A variant of tri-, used for substitutions of three complex rather than simple units, as in,

Etymology

Borrowed from Ancient Greek τρις (tris, “thrice”).