I have been wondering about this little problem for a while now. Everyone understands that, in the binary, the opposite of 'man' is 'woman', and the opposite of 'gentleman' is, namely, 'gentlewoman'.
However, from what I can tell, there seems to be no word that refers to the opposite gender of the word 'lady'. Any ideas?
Etymologically, the male counterpart of lady is lord. Idiomatically, it is gentleman.
Lady comes from an Old English compound noun meaning roughly "loaf kneader," whereas lord comes from a compound noun meaning "loaf keeper" or "loaf protector."
The etymological counterpart of gentleman, which is indeed gentlewoman, is used infrequently these days, usually in historical or quasi-historical contexts.
This is a good example of the etymological fallacy: you often cannot determine what a word means today by looking into its origins.
In addition to 'lord', as pointed out by phoog's excellent answer, there is another male counterpart to the appellation of 'lady': 'gentleman'. Both of these titles refered to members of the petty nobility, which gradually came to refer to members of the well-mannered upper class in general: a wealthy man was a gentleman, and his wife was a lady. Over time, this use was gradually used to refer to more and more people until this class-based definition fell out of use, which is why an announcer at an event might start a speech by addressing those present as "ladies and gentlemen".
