凭空 is an adverb meaning 'without basis' or 'out of thin air'. It modifies verbs to emphasize that an action happens for no apparent reason or without any factual foundation. Common collocations include 凭空捏造 (to fabricate out of nothing), 凭空出现 (to appear out of nowhere), and 凭空消失 (to vanish without a trace). It is more vivid and colloquial than its synonym 无端, and it often carries a connotation of surprising or baseless behavior.