Definitions:

1. Coming before the first in a series, positoned at zero rather than one. ADJECTIVE
   • The programmer explained that the zeroth index refers to the first element in the list.
2. Corresponding to a position preceding the first. ADJECTIVE
   • The zeroth day of the year is January 1st.
3. In the first position in a sequence whose elements are numbered starting at zero. ADJECTIVE
   • The zeroth percentile represents the lowest score in a distribution.

Synonyms:

• nil
• nothing
• null
• zero