Lady Plural. W C Fields Some words do not form their plurals by adding s to the end but by changing their forms eg man becomes men foot becomes feet mouse becomes mice. A singular subject takes a singular verb and a plural subject takes a plural verb.
Similarly the singular possessive for Lady is Ladys and the plural possessive for Lady is Ladies. A polite name for a woman. See subject verb agreement Forming Plurals Table.
Its only a question of degree.
The women in his life do that for him. Some Irregular Plural Forms. The voice of Lady is feminine and the article die. Some nouns cannot be made into plurals just by adding an s es or changing f into a ves.