The word ‘horse’ means any horse, wild or domestic, of either gender. The word ‘mare’ describes a female horse. I guess you know that and want to know the distinguishing difference in terms of anatomy between a horse and a mare. The point is, though, that as mentioned, the word “horse” means both a stallion (a male horse that has not been castrated) and a mare. Therefore you can’t distinguish one from the other because one is part of the other.
I hope that I have explained that adequately. Obviously the distinguishing feature of a male horse is his penis. Anyone, horse expert or not, can see that very readily…as a piece of anatomy which distinguishes the male horse from the female. You don’t need to look for anything else in my opinion 🙂 !
Therefore, I have to conclude that the question in the title is poorly formulated, by which I mean it doesn’t work. I think the question is meant to ask what is the difference between a male and female horse and how you distinguish the difference but I’ve answered that question in very simplistic terms and I think the answer is a good one.
I’ll quickly add the origins of the word “horse” and the word “mare”. It is believed, Dr Desmond Morris says, that the best theory for the origin of the word “horse” is that in ancient times a similar term (perhaps in a foreign language to English) meant “swift” or “running” and that from that word the current name has evolved. Morris says that this is reasonable seeing as the horse was primarily used in the early days as a means of getting around and improving mobility and therefore to refer to the horse as an animal which achieved this is sensible.
The origin of the word “mare” comes from the Anglo-Saxon word “mere” from which we obtained the modern name for a female horse. You can see that there was one evolutionary change in the word, the first ‘e’ being swapped for an ‘a’.
SOME MORE ON HORSES: