Adultery is the social aspect of this area of sin, the lack of concern for family relationships, for social order, for social structure, for faithfuless in relationships.
Fornication is the physical aspect of this kind of sin - the matter of the misuse of the body for a purpose never intended.
Uncleanness is the improper aspect of this kind of sin. It is defiling. It leaves a stain. It is dirty.
Lasciviousness is the loose aspect of this kind of sin. It is a lack of self respect, a lack of discipline, a lack of uprightness. It is wanton.
Acts of sin in this area will incorporate all four of the above, but not necessarily obviously. But in heart, they will all be present if there is sin in this area.
As Jesus says, if a man looks on a woman to lust after her, it is because - first - he committed the social act of disregarding the fact that the woman belonged either to her family or to her husband. She did not belong to him. And therefore it was a sin in heart before the outward movement of the eye.