What are the differences between “Dragonborn”, “Half-Dragon”, and “Draconian” races in D&D?
In the Hoard of the Dragon Queen adventure, for example there is a Half-Dragon npc. I had assumed that when writing the adventure they were only allowed to use known material from Basic, and so renamed the Dragonborn into “Half-Dragon” for the sake of compatibility etc. However, the dragon breath rules are not at all similar for the half-dragon and the dragonborn, and I’ve also noticed wiki article that imply that they are different races entirely. (Thus introducing me to the term Draconian)
Are there clear differences between these three races, (in the same way there are differences between Goblins and Hobgoblins, or Dragonborn and Lizardfolk and Kobolds,) or are they really just three different setting names for the same basic race?
Answers can either be D&D 5e specific, or be based on the lore from all editions of Dungeons and Dragons. (I’m assuming here that the answer will be the same regardless)
Here are two images, the first one is a “half-dragon” from the front of the Hoard of the Dragon queen module, and the second one is a “dragonborn” from the 5e player’s Handbook. I’ve included these images to help explain my confusion.