Female, woman, lady are comparable when meaning a person and especially an adult who belongs to the sex that is the counterpart of the male sex.
Female (the correlative of male ) emphasizes the idea of sex; it applies not only to human beings but also to animals and plants. Its ordinary use as a synonym for woman was once frequent, but this use is now felt as derogatory or contemptuous except in strictly scientific or statistical application, where the term may be employed to designate a person of the female sex whether infant, child, adolescent, or adult.
As compared with woman (the correlative of man, ) which emphasizes the essential qualities of the adult female, lady (the correlative of gentleman ) connotes basically the added qualities implicit in gentle breeding, gracious nature, and cultivated background. Woman is preferred by many whenever the reference is to the person merely as a person.
Lady, on the other hand, is preferred when exalted social position or refinement and delicacy are definitely implied, but lady may also be used informally as a mere courteous synonym for woman, though its indiscriminate substitution for woman (as in wash lady , saleslady ) carries courtesy into travesty.