zì rán ér rán
involuntary
automatically
jiá rán ér zhǐ
with a grunting sound it stops (idiom); to come to an end spontaneously (esp. of sound)
yóu rán ér shēng
arising involuntarily (idiom); spontaneous
to spring up unbidden (of emotion)
bù qī rán ér rán
happen unexpectedly
turn out contrary to one's expectations
huò rán ér yù
to recover speedily (idiom); to get better quickly
zhī qí rán ér bù zhī qí suǒ yǐ rán
to know that it is so but not why it is so (idiom)