道 dào - measure word

道 measure word for long things

一道 [yī dào] a course of a meal; a question; an order; a streak of light; a crack; a door; a line of defense

一道: a course of a meal

一道菜 [cai] a course of a meal

一道美味 [měi wèi] a course of delicious food

一道: a question

一道难题 [nán tí] a difficult question

一道数学题 [shù xué tí] a math problem

一道: an order

一道命令 [mìnɡ lìnɡ] an order

一道: a streak of light

一道缝 [fènɡ] a crack; a gap

一道亮光 [liànɡ ɡuānɡ] a streak or flash of light

一道闪电 [shǎn diàn] a bolt of lightning

一道: a line of defense

一道防线 [fánɡ xiàn] a defensive line

一道封锁线 [fēnɡ suǒ xiàn] a blockade line

一道路障 [lù zhànɡ] a roadblock

一道墙 [qiánɡ] a wall

一道铁丝网 [tiě sī wǎnɡ] a barbed wire fence

一道门 [mén] one of a series of entrance doors or gates 

一道 [yī dào] and 一扇 [yī shàn] are sometimes interchangeable when talking about a door or screen.

—道 [yī dào] implies a barrier: —道门 [yī dào mén, a door]; 一道屏风 [yī dào pínɡ fēnɡ, a screen]; —道墙 [yī dào qiánɡ, a wall].

一扇 [yī shàn] refers to something that has a frame and is moveable: 一扇门 [yī shàn mén, a door]; —扇窗户 [yī shàn chuānɡ hu, a window]; 一扇屏风 [yī shàn pínɡ fēnɡ, a screen].

(Never —扇墙 or —道窗户)