Regional Rapid Service; Section Rapid Service
A JR West train service that operates as a local train on some sections and as a rapid service on others. The English name 'Regional Rapid Service' is the official JR West designation.
I took the Regional Rapid Service from Osaka to Himeji.
The Section Rapid Service stops at every station from a certain point along the route.
A general rapid service train that skips some stations, while 区間快速 specifically refers to a JR West service that changes its stopping pattern mid-route.
A local train that stops at every station, unlike 区間快速 which runs express on part of its route.
Compound of 区間 (section, interval) and 快速 (rapid service), reflecting the train's operation as a rapid service only on certain sections of the line.