Accordingly to the player handbook dragonborns are an own race originated by dragons. But I'm uncertain about half-dragons. Are they dragonborns themselves or are they a mix between dragons and other humanoids?
If they are not the same:
- Do they differ in appearance (e.g. can half-dragons have tails or wings?)?
- Could an adventurer (or townsfolk) differ them?
Background: I stumbled upon half-dragons in Hoard Of The Dragon Queen and one of the PCs is a dragonborn, so I'm wondering if it is the same or rather what are the differences.