The Cleveland Plain Dealer had a story about three men who started a business hosting different kinds of networking events for people. They called their venture “3 Guys”.
But later they took on a woman as a partner and now their business is called “3 Guys & A Lady”.
The incongruity of the juxtaposition of the casual word ‘guy’ with the much more formal ‘lady’ is immediately apparent. But what is also clear is that once they had chosen the word ‘guys’ for themselves they were in a bind as to how to incorporate women into the mix. “3 Guys and a Woman” sounds wrong.
There really is no female equivalent for ‘guy’ that captures the same spirit of informality while not being insulting or disrespectful or even offensive. The closest is ‘gal’ but that sounds too old-fashioned and can be seen as demeaning.
I have sometimes seen the plural ‘guys’ used to encompass mixed gender groups but only on rare occasions in the phrase ‘you guys’ but it always felt a little awkward. I don’t think that “4 Guys” would have worked here.