The word "lack" has multiple meanings, depending on its context.
1) If used as a verb, it means to be deficient or lacking in something; for example, "I lack experience."
2) As an adjective, it can refer to the absence of something; for instance, "There is a lack of water in this region."
3) In its noun form, it signifies the state of being without something that is needed or desired; as in, "The community lacks resources for education."