Real Dictionary

lack
If there is a lack of something, there is not enough of it or it does not exist at all.
verb: If you say that someone or something lacks a particular quality or that a particular quality is lacking in them, you mean that they do not have any or enough of it.

lack in American English
the fact or condition of not having enough; shortage; deficiency
to be deficient in or entirely without
to be wanting or missing; show a deficiency
intransitive verb: to be absent or missing, as something needed or desirable
noun: deficiency or absence of something needed, desirable, or customary
transitive verb: to be without or deficient in

lack in British English
noun: an insufficiency, shortage, or absence of something required or desired
verb: to be deficient (in) or have need (of)

lack- in American English
lacking