1.
section; segment; interval (of a route or range)
A defined portion of a route, track, or range, often used for transportation routes, distance measurements, or mathematical intervals.
この区間は工事中だ。
This section is under construction.
東京から大阪までの区間は約500キロある。
The section from Tokyo to Osaka is about 500 kilometers.
高速道路の一部の区間で速度制限が変更された。
The speed limit was changed on some sections of the expressway.
Common collocations: 区間運転 (service on a limited section of a train line), 区間快速 (semi-rapid train that runs express on a limited section). In mathematics, 区間 refers to an interval on a number line. Often appears on train signs and announcements to indicate which portion of a route is affected by delays or service changes. Related: 区域 (area, zone — refers to a two-dimensional area rather than a linear section).