also: わたりま
noun
span; distance between two points; distance between supports
Technical term used in architecture and civil engineering for the span of an arch, bridge, or similar structure; also refers to the distance between two points in general.
この橋の径間は50メートルです。
The span of this bridge is 50 meters.
アーチの径間を測る。
Measure the span of the arch.
スパン is a more common loanword for 'span' in everyday contexts, while 径間 is a technical term used mainly in engineering.
Compound of 径 (path, diameter) and 間 (interval, space), referring to the distance or span between two points.