IPA: /ˌɪntəˈrɪdʒənl/
KK: /ˌɪntərˈridʒənl/
Relating to or connecting different regions, often used to describe activities or movements that occur between these areas.
The interregional conference brought together leaders from various parts of the country.
Interregional → It is formed from "inter-" (meaning between) and "regional" (from Latin "regio", meaning region). The word describes something that occurs between different regions.
Think of things that happen 'between' ('inter-') different 'regions' — that's what interregional means.