trit·i·um 
(trĭtē-əm, trĭshē-)
(trĭtē-əm, trĭshē-)n.
A rare radioactive isotope of hydrogen, H-3, having one proton and two neutrons in the nucleus and a half-life of 12.3 years, prepared artificially for use as a tracer and as a constituent of hydrogen bombs.
[From Greek tritos, third; see trei- in the Appendix of Indo-European roots.]
- superciliary
- supercilious
- superciliously
- superciliousness
- superclass
- supercluster
- supercoil
- supercollider
- supercolony
- supercomputer
- superconduct
- superconducting
- superconductive
- superconductivity
- superconductor
- supercontinent
- supercool
- supercritical fluid
- supercurrent
- superdelegate
- superdense
- superdominant
- superduper
- superego
- supereminence