mainline

正常的；主要的；标准的。

Normal, principal or standard.

属于或关于铁路主线路的。

Of or pertaining to the principal route or line of a railway.

属于或关于地面重型铁路系统的,区别于地下、高架或轻轨的。

Of or pertaining to a surface-level heavy rail system as distinct from an underground, elevated or light rail one.

属于或关于国家或长途铁路网络运营商的,区别于城市和郊区运营商。

Of or pertaining to national or long-distance rail network operators as opposed to urban and suburban operators.

关于两个主要港口之间的直达航线。

Pertaining to a direct route between two major ports.

属于开局主线(标准最佳走法序列)的。

Of a sequence of opening moves: being part of a main line ("a standard sequence of opening moves considered to be best play").