Lack, want, dearth, absence, defect, privation are comparable when denoting the fact or state of being without something.
Lack is somewhat ambiguous in scope since it may imply either a total or a partial failure of something that in the circumstances might be expected to be present and often requires qualification to make its intent unequivocal.
Want (see also POVERTY ) may imply either a partial or a complete lack but its range of application is far narrower than that of lack since it specifically applies to deficiencies of what is essential or at least needed or desirable; thus, one may exhibit either a want or a lack of tact; there may be a complete lack , rather than want, of pain immediately after some injuries.
Dearth implies an often distressingly inadequate supply rather than a complete lack.
Absence is perhaps the most unequivocal of these terms; when not qualified it denotes the complete lack of something or that something or occasionally someone is not present.
Defect (see also BLEMISH ) implies the absence or lack of something required for completeness (as in form) or effectiveness (as in function).
Privation in the sense pertinent here (see also POVERTY ) is used primarily in certain philosophical definitions of negative qualities or states as absences of the corresponding positives.