You can prove someone is a woman, but you cannot prove she’s a lady. I clearly remember my college journalism professor teaching us this little writing mantra.
What constitutes a lady is dependent upon who you ask, making it an arbitrary and editorial word. What makes someone a woman is much more concrete. Therefore, when writing about women, be sure to address them as such.
This rule typically arises when writing about social organizations for women, like sororities.
An incorrect example: The ladies of Gamma Phi Beta hosted the event.
Correct the sentence by writing: The women of Gamma Phi Beta hosted the event.
In related writing rules, you do write “first lady” when referencing a woman with that title. But it is a courtesy title, not a formal one. Therefore, first lady never is capitalized, even when it comes before a name.
For example, First lady Michelle Obama spoke at the event.
Pretty simple, right? Now go forth and use words correctly!