When talking to a horse I belive that the tone of voice is the main factor of comprehension. In France the "Hyah" would probably sound more like Hi-a to you (if you're an English speaker)
Cheval means horse in french!!
male horse in french is... cheval mâle
cheval
J'ai un cheval.
Une hippocampe
Le Cheval Shop
House = Maison Horse = cheval
Plumes de cheval.
Un cheval vert.
un cheval de course
un cheval à bascule
une randonnée à cheval