‘凭空’ literally combines ‘凭’ (to rely on, to base on) and ‘空’ (empty, sky, void), forming an adverb meaning ‘out of thin air’ or ‘without any basis or evidence.’ It conveys that something appears, is claimed, or is invented with no foundation in reality, logic, or observable facts. The phrase carries a slightly skeptical or critical tone — it’s often used to question the validity of an assertion, accusation, or explanation.

This expression is common in both spoken and written Chinese, especially in debates, news commentary, or everyday reasoning. While it can describe physical phenomena (e.g., something seemingly appearing from nowhere), its dominant use is abstract: referring to unsupported claims, unfounded suspicions, or baseless assumptions. It’s not used for neutral or positive creation (e.g., artistic inspiration), but rather emphasizes lack of justification or evidence.