Used before a verb to indicate that an action or situation occurs suddenly or unexpectedly.

to clamor or cause a noisy disturbance; rowdy horseplay; specifically used in patterns like 起哄 qǐ​hòng

Used in certain constructions to indicate that the second action or state follows immediately from or is the result of the first, as in 一 yī...ér...

to climb; to board a vehicle; to mount; to go to a place