Usage patterns
直線を引くto draw a straight line
I drew a straight line in my notebook to make a graph.
〈物〉と〈物〉を直線で結ぶto connect two points/things with a straight line
I connected point A and point B on the map with a straight line.
直線に進むto go straight ahead, to move in a straight line
This road goes straight ahead for a while.