classifier for long thin things (rivers, cracks etc), barriers (walls, doors etc), questions (in an exam etc), commands, courses in a meal, steps in a process
province (of Korea or Japan)
channel
method
doctrine
teachings
呀
haa1
(particle equivalent to 啊 after a vowel, expressing surprise or doubt)
Learn Stroke Order
See how to write "知不知" with stroke-by-stroke animation