In the first position in a sequence whose elements are numbered starting at zero; the ordinal number corresponding to zero. (adjective)
Corresponding to a position preceding the first. (adjective)
Examples of word zeroth
The previously discussed omnidirectional patterns are also called zeroth-order patterns and the other patterns mentioned previously (dipole and cardioid) are called first-order patterns.
For the sake of simplicity the inorganic can be taken to include the quantum level, although perhaps this level could constitute its own 'zeroth' level.
Thus the year in which his father died was his "zeroth" year.
If Jehoiachin had been held captive for thirty-seven years before the accession of Evil-Merodach, then "the thirty-seventh year" would have to be the thirty-seventh year following a "zeroth" or "starting" year.
What cannot be seen is the hierarchically "zeroth" highest part, the root.