Due their Draconic ancestry, Half-Dragons are a hardy and long lived race.  Due to their longevity, they have a greater chance to increase their knowledge and learn to apply it.

Constitution score increases by 2. Intelligence and Wisdom scores increase by 1.

Can read and speak Common, Draconic, and the language of the non-draconic parent.

By their nature, Half-Dragons do not derive all of their traits from the dragon that spawned them.  They also take on aspects of the other race that birthed them.  Half-Dragons gain the following benefits:

1. Can read, write, and speak the language of their non-dragon parent.
2. Gain a racial trait of that same race.

The following is a list of races and their attached benefits (Players Handbook pages included for reference)

• Dwarf: Dwarven Resilience; read, write, speak Dwarvish. (PHB 20)
• Elf: Trance; read, write, speak Elvish (PHB 23)
• Halfling: Lucky; read, write, speak Halfling (PHB 28)
• Human: Ability Score Increase; read, write, speak common (PHB 31)
• Gnome: Gnome Cunning; read, write, speak Gnomish (PHB 37)
• Half-Elf: Skill Versatility; read, write, speak Elvish (PHB 39)
• Half-Orc: Savage Attacks; read, write, speak Orc (PHB 41)
• Tiefling: Infernal Legacy; read, write, speak Infernal (PHB 43)

You are the child of a dragon, the most ancient and deadly of the intelligent creatures.  You gain the following benefits of that heritage:

1. Vision (Monster Manual 180)
   1. Darkvision (60ft)
   2. Blindsight (10ft)
2. Elemental Breath Weapon equivalent to the Wyrmling of the color that sired you (MM 180): 
   • Black (MM 88): 15ft x 5ft line Acid damage
   • Blue (MM 91): 30ft x 5ft line Lightning Damage
   • Green (MM 95): 15ft cone Poison Damage
   • Red (MM 98): 15ft cone Fire Damage
   • White (MM 102): 15ft cone Cold Damage
   • Brass (MM 106): 20ft x 5ft line Fire Damage
   • Bronze (MM 109): 40ft x 5ft line Lightning Damage
   • Copper (MM 112): 20ft x 5ft line Acid Damage
   • Gold (MM 115): 15ft cone Fire Damage
   • Silver (MM 118): 15ft cone Frost Damage
3. Elemental Resistance: You gain resistance to the damage your dragon parent represents.
   • Cold: White and Silver
   • Fire: Red, Brass, and Gold
   • Lightning: Blue and Bronze
   • Acid: Black and Copper
   • Poison: Green