singular: woman plural: women there's no parlance of womens'.

The position of the apostrophe indicates possesion, and woman is singular, women is plural (more than one) For example The woman's dress (Who owns the dress, the woman) The womens' dresses (Who owns the dresses, the women). If there is more than one woman (women) then the apostrophe should be after the "s". However in modern English it is rarely used. Unless you are taking a grammar exam, you can safely not use it without lessening peoples understanding of your writing, especially the second example (womans'). Many English writers only use the first type (woman's) both correctly and incorrectly.

women's = 女人们的