There are four very different words that all translate into dragon. Their Serbian versions are: Zmaj, Ala, Aždaha/Aždaja and Lamja. Shapeshifters one and all. in Balkan Slavic mythologies Dragons start out as either snakes or carps (Croatians also believe wels catfish can do this too) that then "reveal their legs" after around 10/12/30/33/40/50/100 years and become adult Dragons. So juvenile Dragons look just like snakes/carps and then undergo a metamorphosis into adult dragons. Or they are especially powerful Silvan herd dogs that become a zmaj trough the nobility of their spirit and the endurance of their loyalty.
Zmajevi (plural of zmaj) are the good, noble dragons. Think metallic dragons from DnD in character, but the appearance of either the stereotypical fantasy dragon or a flaming bird with a snake's tail. There are no half-dragons/polu-zmajevi with humans. Any child born from a union of a zmaj and a human woman is human and also a hero while any child born of a union of a human man and a zmaj is a zmaj. The pregnancy with a zmaj child is difficult for a human woman, lasts 15-20 months and the birth can kill them. Zmaj is treated as gender neutral, but I've never heard someone say zmaj man/male, but I have heard of people saying zmaj woman/female as a descriptor of a woman's fierceness or other such "male" qualities.