- TycheThe goddess of luck/fortune; counterpart of the Roman Fortuna.
- tychismA theory suggesting that absolute chance, or indeterminism, is a real factor operative in the universe.
- tychoparthenogenesisparthenogenesis in a species that normally reproduces normally (typically a weevil)
- tychoparthenogeneticRelating to, or by means of tychoparthenogenesis
- tychoplanktonAny benthic organism found amongst plankton because of sea currents etc.