Meanings

vertex normal

edgetype

heavy line (for emphasis)

thin line

death ray

linearity

Western Front (of WWI)

boundary line

branch line

ordinary ray

wire rod

undersea cable (communications, power)

measuring line (surveying)

military demarcation line

printed wiring board

tropics (of Cancer and Capricorn)

line integral

to be on the right track

hard line

Sōbu Line (Chiba-Tokyo railway)