lack

To lack something is not to have a thing you need or ought to have. A soup that lacks salt, a flat that lacks a proper window, an argument that lacks a shred of evidence.

The noun is the commoner half, and it nearly always takes OF: a lack of sleep, a lack of money, a lack of interest, 'for lack of a better word'. Grammar trap: the verb takes no preposition — he lacks confidence, never 'he lacks of confidence' — while the noun demands one. Lacking works as an adjective and takes IN: lacking in detail, lacking in confidence. Lack carries a judgement inside it, not just an absence, because it says the missing thing was wanted — which is why nobody writes that a fish lacks legs. It is a plain but slightly formal verb; in speech people say has not got or is short of.