In Defense Position (called Defense Mode in the anime), a Monster Card can be either face-up or face-down, in a Horizontal Position. In this position, the DEF value is used to represent this card, except where a card effect requires a specific examination of the ATK value.
In Defense Position, a Monster Card is always in a Horizontal Position. When a monster is "Set", it is played in face-down Defense Position. Monsters cannot be Normal Summoned in face-up Defense Position, except by a card effect that allows them to be summoned that way (such as "Light of Intervention"). During battle between a Defense Postion monster, the DEF value of that monster is used to calculate Battle Damage, rather than the ATK value.
In the Yu-Gi-Oh! 5D's anime, Defense Position monsters become blue-colored.
Types of Monster Cards
Types of Spell Cards
Types of Trap Cards
Other Types of Card
ATK - DEF - Level - Attribute - Type
Playing Field Zones
Types of Summon
Types of Monster Effects
Types of Effect Monsters
Types of Spell Speed
Aqua - Beast - Beast-Warrior - Dinosaur